1

It has long been known that the sea otters living along the West Coast of North America help keep kelp forests in their habitat healthy and vital

A. NO CHANGE

B. living along the West Coast of North America, they help

C. that live along the West Coast of North America and help to

D. that live along the West Coast of North America, where they help

Here, B can be eliminated because it creates a comma splice. D can be eliminated because it converts an important information in the sentence as non-essential.

Now, when it comes to picking between A nd C, A I thought could be eliminated because it doesn't encloses the non-essential information in a comma pair.

C seems to be okay. However, the correct answer is A. Does it means that all the sentences which come after that need to be a complete clause with a subject and a verb? As in the given question, "and help" have no subject to refer to; maybe it refers to "that," acting as the subject.

Please explain me this question.

  • Yes. "That" is a clause subordinator - it introduces clauses. That the sea otters living along the West Coast of North America help keep kelp forests in their habitat healthy and vital is a clause. – BillJ Apr 27 '18 at 9:17
  • You don't need to surround living along the West Coast of NA with commas as that's "essential" information; i.e., it's those sea otters that live along the West Coast, not some other group (living elsewhere). (If you go to Wikipedia, you'll find that sea otters' habitat isn't restricted to NA.) They help keep forests healthy is grammatical – help keep is the usual way to put it, though you could insert a to and make it help to keep with no change in meaning. – userr2684291 Apr 27 '18 at 10:20
1

"That" can be a pronoun, determiner, adverb, or conjunction. When it's used as a conjunction, it does need a complete clause. In its other meanings, it doesn't. For instance "Is that hot?" is perfectly fine.

Now, when it comes to picking between A nd C, A I thought could be eliminated because it doesn't encloses the non-essential information in a comma pair.

I don't think "essential" is the best term. The question is whether it is restrictive. The phrase "living along the West Coast of North America" is restrictive; it restricts the subject from sea otters in general to a subset of sea otters. Restrictive clauses should not be set off with commas.

Does it means that all the sentences which come after that need to be a complete clause with a subject and a verb?

When you're talking about a word, rather than using the word, it should be set off from the other words somehow, e.g.

Does it means that all the sentences which come after "that" need to be a complete clause with a subject and a verb?

I don't know of a way to do sentence diagrams in SE, so I'll just use parentheses:

It has long been known (that the sea otters (that live along the West Coast of North America, (where they help keep kelp forests in their habitat healthy and vital)))

Here, "where they help keep kelp forests in their habitat healthy and vital" is a subordinate clause to "the West Coast of North America".

"(that live along the West Coast of North America, (where they help keep kelp forests in their habitat healthy and vital)))" is a restrictive clause modifying "sea otters". So the entire passage "the sea otters (that live along the West Coast of North America, (where they help keep kelp forests in their habitat healthy and vital)))" is a noun phrase; it introduces the phrase "sea otters", then further describes what sea otters they're talking about. The important part is that In Option $D$, everything that follows "sea otters" is modifying "sea otters". While there are verbs in that description, they are in subclauses, and none of them have "sea otters" as a subject. So for the purpose the analysis, we can replace "the sea otters ..." with "certain sea otters".

Now the sentence becomes "It has long been known that certain sea otters". That's the entire sentence. Remember, everything else in the sentence is just saying which sea otters they're talking about. This then is a sentence fragment; it doesn't present a complete thought that can be the object of the verb "known".

-1

While many English classes seem to teach the use of commas as immutable grammar rules, this is misleading. Commas are almost always optional, and are used to separate parts of a sentence to make it easier to understand. They also mimic the pauses introduced when speaking the sentence out loud.

So when you say:

A I thought could be eliminated because it doesn't enclose the non-essential information in a comma pair.

it suggests you've been taught a "rule" that simply isn't valid. It's a good practice to enclose nonessential information in a comma pair, because it helps the reader understand your logic, but it's not required.

For example, I could have written the previous sentence as:

It's a good practice to enclose nonessential information in a comma pair because it helps the reader understand your logic but it's not required.

Poor writing style, yes, but grammatically OK.

In your example sentence "living along the West Coast of North America" is an adjectival phrase modifying "otters". "In their habitat" is another such phrase modifying "kelp forests". You could exclude both without significantly affecting the main point of the sentence:

[Some] sea otters help keep [some] kelp forests healthy and vital.

It is grammatical to start the adjectival phrase with "that":

[The] sea otters that live along the West Coast of North America help keep ...

Answer choice C changes the entire sentence into a fragment because it combines everything after "otters" into a long adjectival phrase. We never find out what is known about the otters. A similar example:

The man living in that house and who helps his neighbor with her shopping.

The man ... does what? The sentence never resolves. Grammatical version:

The man living in that house helps his neighbor with her shopping.

  • "Commas are almost always optional, and are used to separate parts of a sentence to make it easier to understand." No. Commas convey grammatical meaning. – Acccumulation Apr 27 '18 at 15:17
  • @Acccumulation If you provide an example of a comma used as a grammar "rule", I bet I can provide a counter-example to show your assumption is incorrect. – Andrew Apr 27 '18 at 15:55
  • A claim based on years of observation and multiple statements by experts is not a "assumption". One rule is that commas mark phrases as non-restrictive. I don't see what "providing a counter-example" would mean: you could provide a sentence and assert that it does not follow that rule, but then I can just assert that it's wrong. – Acccumulation Apr 27 '18 at 16:20
  • @Acccumulation The restrictive/non-restrictive use of commas is syntactical, not grammatical -- it conveys information, but if you fail to use the comma, it doesn't make the sentence incorrect. Example: Edgar Allan Poe who wrote "The Raven" is a great American poet. Poor style, yes, but grammatical. See this source, and I quote, "Nonrestrictive modifying clauses are usually set off by commas" (meaning they don't have to be). – Andrew Apr 27 '18 at 17:31
  • @Acccumulation but as I said if you can give me a example (with sources) that shows when commas are required as a grammar rule, I'll accept it. – Andrew Apr 27 '18 at 17:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.