What did he do that was so wrong?

Why don't you say that without 'that'? I asked this somewhere else a few months ago, and got an wonderful answer. I thought that was reasonable enough. The answer said that you always need a subject for every verb, and if you take away the 'that', then the sentence would lack the subject for 'was'.

But see this example below.

Who do you think work the most?

Here, doesn't 'who' work as the subject for 'work' properly? Why do natives say this without 'that' when you say the very first sentence always with 'that'?

  • 2
    In your first example, "that was so wrong" is a relative clause, and since "what" is its subject, it cannot be omitted. In your second example, "work the most" is not a relative clause but a declarative content clause in which "that" is omissible.
    – BillJ
    Jun 7, 2019 at 16:55
  • 2
    It should be works in your second example, not work. But it's not the what/who switch making the difference here. There's no that in What do you think was so wrong?, for example, and we do normally include it in Who is it that works the most? Jun 7, 2019 at 17:00
  • You can, however, omit the phrase that was: What did he do so wrong? Jun 7, 2019 at 19:07

2 Answers 2


[1] What did he do [that was so wrong]?

[2] Who do you think [works the most]?

In [1] "what" is object of "do" and subject of the bracketed relative clause. "That" is not omissible if it is subject of a relative clause, as it is here.

In [2] "who" is object of "think" and subject of the bracketed clause, though it is not a relative one but a declarative content clause where this time "that" is omissible.

Incidentally, the default value for "who" in [2] is singular, i.e. "works", but it can, however, be overridden when there is a presupposition that the answer is plural, in which case "work" is acceptable

  • Thank you very much :D, but I still didn't get it. If you don't mind may I ask you for more? So, you said that the 'that' in [2] is omissible, which means that [2] is actually "Who do you think that works the most?", right? Then, how should I think that one is a relative clause and the other is not, when both of them have the same structure as "interrogative + do verb + subject + verb + that + verb + adverb"?
    – dolco
    Jun 7, 2019 at 19:24
  • They don't have the same structure. Relative clauses have antecedents and (typically) function as modifiers of nominals. In [1] "what" is the antecedent that is modified by "that was so wrong". Content clauses, by contrast, don't have antecedents and they function as complements, not modifiers. In [2] the content clause "works the most" is complement of "think".
    – BillJ
    Jun 8, 2019 at 6:03

Think of it in this context:

  • What did he say that made you change your mind?

That what he said made you change your mind!

  • Is this really an answer? thanks for it anyways, but that does not answer the why IMO.
    – Cardinal
    Jun 7, 2019 at 16:17
  • @Cardinal Definitely not, I'm still looking for an explanation in grammar. Jun 7, 2019 at 16:19

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