Read the sentence and answer the question. They ate lunch in the restaurant and then they took their dog for a walk in the park. Which correctly shows where a comma is needed in the sentence?

A. They ate lunch in the restaurant, and then they took their dog for a walk in the park.

B. They ate lunch in the restaurant and then they took their dog, for a walk in the park.

C. They ate lunch in the restaurant and then they took their dog for a walk, in the park.

D. They ate lunch in the restaurant and, then they took their dog for a walk in the park.