Question

Which sentence shows correct subject-verb agreement?

There's a good answer to that question.
There're a good answer to that question.
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Answer 1

The first one is correct. The second one wouldn’t make as much sense. “There are a good answer to that question” is a grammatical error.

Answer 2

The first sentence.

This is because "There's" means "there is" which makes more sense than putting "There're" because that would mean "there are".

Hope this helps :)