1. It is fun to talk with foreigners.
  2. Do you have something to eat?
  3. This is a deep lake to swim.
  4. She must be warm-hearted to help you.
  5. She lived to be ninety.

On the answer sheet, the answer is number 3. but I don't agree with that answer because it is a correct sentence in dictionary opinion that "I swam a lake". Thus number 3. is OK.

I think the incorrect sentence is number 4. because there must be a noun after "warm-hearted". Thus I can correct this sentence to "She must be warm-hearted person to help you."

Regarding number 5.: is she still alive or dead?

  • 1
    All of those sentences are grammatical. Dec 24, 2015 at 17:44
  • 3
    #3 is an odd duck semantically. It does not quite follow the "This is a hard problem to solve" pattern, or the "This is a fast road to take" pattern. Changing deep to cold would work better, for example.
    – TimR
    Dec 24, 2015 at 18:00
  • 1
    But it's possible to understand it to mean, "Are we sure we want to swim in this lake? It's really deep."
    – TimR
    Dec 24, 2015 at 18:06
  • 2
    Hey is this a trick question? The only ungrammatical sentence I see here is your title. :)
    – M.A.R.
    Dec 24, 2015 at 18:29
  • 2
    3 is not incorrect, but weird, because swim a lake would more easily mean crossing it swimming, and the depth is hardly relevant. a wide lake to swim would work better.
    – njzk2
    Dec 24, 2015 at 19:32

3 Answers 3


The answer key is not correct in terms of grammaticality, but unfortunately more context is needed.

"Swim" can be used transitively to mean that you are traversing/going a certain distance in something by swimming; as in swimming a lake to get to the other side as part of a race.

But the answer key finds it awkward. It would prefer you to put a preposition "in" after "swim"; the typical meaning is that you move around (without extended contact with the bottom) in some aquatic body, that you swim in. e.g.

I swam in the lake yesterday.

The answer key seems to think that the third sentence means "the lake is too deep for swimming".

For number 4, "be" links the adjective "warm-hearted" to the pronoun "she". Another example:

I am angry at your misdeeds.

For number 5, she is dead. If she was still alive we would say "she is ninety years old" or some variation.

  • 1
    You can certainly swim a lake. It means to cross the lake by swimming.
    – TimR
    Dec 24, 2015 at 18:07
  • Yes, but that isn't what the homework question meant. I would prefer using "swim across a lake" for that. Dec 24, 2015 at 18:07
  • We don't know what the homework question meant. It could mean "The challenge this lake presents to the person who would swim it is its great depth. Get a cramp, you can't stand up; and if you sink, you'll sink beyond rescue."
    – TimR
    Dec 24, 2015 at 18:10
  • Context unavailable then. Rewriting half my answer to accomodate. Dec 24, 2015 at 18:10
  • So then, 'deep' is unseemly to use a transitive verb but i guess when 'deep' replace to 'too distant' the answer key don't think it awkward. right? by the way, in number 4, does she yet help me? and she would help me warmly? thank you for answer. :)
    – inches
    Dec 24, 2015 at 18:42

This may be a regional thing (I'm from London) but I definitely find sentence 3 odd:

This is a deep lake to swim

As another answerer has already mentioned, I would generally expect to see:

This is a deep lake to swim in.

And I confess I was quite surprised to see how many people found the original sentence natural.

It is certainly true that you can swim 100 metres, but I don't think I'd ever say "I swam a lake" to mean "I swam the distance of a lake." I might say "I swam the width of a lake", "I swam the breadth of a lake", "I swam the length of a lake" or something like that, but it's unlikely. If I meant that I swam from one end of the lake to another, what I would usually say is "I swam across a lake."

So the other alternative I would prefer is:

This is a deep lake to swim across.

  • 3
    I don't think that people necessarily found the original sentence "natural," but I think they found it "acceptable." It might be a little unusual, but not to the extent where it violates grammatical standards. In other words, I agree with your suggested improvements, but I would disagree with the test writers if they indeed meant to imply that Sentence #3 was "grammatically incorrect."
    – J.R.
    Dec 25, 2015 at 12:21
  • Being from London, you've surely heard of people "swimming the channel," right? Jan 26, 2016 at 2:44
  • @DanielMcLaury Yes I have, it's true. But then I've also heard of people "running the marathon", but I'd still be very unlikely to say "that's a long road to run", or "that's a long track to run" or "that's a wide park to run" and so on and so forth
    – Au101
    Jan 26, 2016 at 3:40
  • "Long road to run" has a whole bunch of google hits, even once you filter out everything about the Foo Fighters song "Long Road to Ruin." Jan 26, 2016 at 3:43

All five sentences are grammatically correct. Sentences #3 and #4 are the trickiest.

These two sentences are perfectly idiomatic:

. 2. Do you have something to eat?
. 5. She lived to be ninety.

Sentence 5 implies that "she" is dead. "She's ninety" or "She has lived to be ninety" or "She's looking forward to her ninety-first birthday in June" are things people might say if "she" is still alive.

The remaining three sentences start with an idiomatic sentence. They add a detail, in a grammatically correct way:

  1. It is fun to talk with foreigners.

This sentence combines "It is fun to <infinitive verb>" with an adverbial phrase that provides an indirect object.

  1. This is a deep lake to swim.

This sentence combines "This is a dangerous thing to do" with "This is a deep lake", "This is a place to swim", and "Some people can swim across this lake". You can imagine this sentence being built up in the following steps:

  • "This is a dangerous river crossing."
  • "It is dangerous to ford this river."
  • "This is a dangerous river to ford."
  • "This is a deep river to swim."
  • "This is a deep lake to swim."
  1. She must be warm-hearted to help you.

This sentence combines "She must be nice." with "She went out of her way to help you", "She was happy to help you", and "Only a very nice person would help you." It substitutes "warm-hearted" for "very nice".

Notice the difference between:

She must be nice.

She must be a nice person.

Changing the predicate from an adjective to a noun phrase requires adding a determiner (such as the indefinite article "a").

Also notice the difference between:

She must be {very nice / warm-hearted} to help you.


{She must be glad / It must warm her heart} to help you.

The first pair of choices say that "We know that she is a very nice person, because only a very nice person would help you." The second pair of choices say that "Helping you makes her feel good."

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