A complex sentence contains one independent clause and at least 1 dependent cause. Which option is a complex sentence?

Question

The lifeguard at the town pool is Christina.
After swim team practice, Christina's best friend drives her home.
Christina learned to swim when she was 3, and now she's the captain of the high school swim team.
Christina has been a swim instructor for 3 years, so she has a lot of experience working with kids.

Answer 1

The option that contains a complex sentence is:

"Christina learned to swim when she was 3, and now she's the captain of the high school swim team."

In this sentence, "when she was 3" is a dependent clause that provides additional information about the time when Christina learned to swim. The rest of the sentence is an independent clause.

The other options do not contain dependent clauses.