Which sentence combines these two sentences and includes a relative clause?

Question

The twins pretended to be each other. The switch was a huge mistake.

Choices

The twins pretended to be each other, which was a huge mistake.

The twins pretended to be each other, a huge mistake.

The twins pretended to be each other because they made a huge mistake.

The twins pretended to be each other, and it was a huge mistake.

I looked up relative clause, but still not sure I understand what a relative clause is.

I am thinking the first sentence, but the last one might be the better choice. Just not sure from what I looked up.

Answer 1

the first one is correct. It contains a relative clause

#3 also has a subordinate clause, but not a relative clause. Relative clauses are clauses starting with the relative pronouns who/whom, that, which, whose, where, when.

The last one is just a compound sentence, with two independent clauses separated by "and"

Answer 2

Yes, the first sentence has a relative clause.

This is my favorite grammar site.

http://www.chompchomp.com/terms/relativeclause.htm

Answer 3

Thank you both and thanks for the link