Question: Which of the following sentences uses a comma correctly?

Options:

1. I went to the store, and bought milk.
2. She said she would come, but she didn\'t.
3. He likes to swim, run and bike.
4. They are going to the park, and to the beach.

Correct Answer: She said she would come, but she didn\'t.

Solution:

The second option correctly uses a comma before the conjunction \'but\' to separate two independent clauses.