Silly questions, like X is/are a complete waste of time?

Question

I'm stumped with this one. Given the question, "What did you learn from doing this task?", which of the following answers is correct?

1. That silly questions, like "What did you learn from doing this task?" is a complete waste of time.
2. That silly questions, like "What did you learn from doing this task?" are a complete waste of time.

I know the latter is technically correct, but the first answer also "sounds right"!

Answer 1

To answer your question directly, "questions" is plural and so should always have a plural verb ("are"). However, there are two other issues with your sample answer:

1. Your are eliding the main subject and verb from your answer. This makes the sentence potentially hard to read, and ungrammatical in a formal setting. (In some kinds of writing/speaking it would be acceptable).
2. You need a comma after the quotation.

I learned that silly questions, like "What did you learn from doing this task?", are a complete waste of time.

The rule for the subordinate parenthetical clause in the middle of your sentence is that it can be removed without affecting the meaning or structure of the sentence.

I learned that silly questions ... are a complete waste of time.

This makes it more obvious that you need to use the plural verb "are". It also makes it clear that your subordinate clause should be framed by two commas, and not just one.

Answer 2

Ditto JLG and Shiny. Let me just add: When you are confused by a complex sentence, it often helps to try dropping out modifiers and clauses that are irrelevant and see what's left. To take this sentence as an example, the words between the commas do not affect any attributes of the subject and verb. So try just dropping them out and see what you have left. Namely, "That silly questions is/are a complete waste of time." It is more likely to then be obvious that the correct verb is "is".

Unless you are concerned about a subordinate clause or prepositional phrase or whatever itself, if you are just looking at subjects and verbs, the "right answer" should be unaffected by dropping out the clutter. Similarly for long adjective phrases, etc.