PLZZ HELP ASAP!!!!
Which sentence contains an adverb clause?

A.
When you return from California, take a taxicab from the airport.

B.
California has three of the top ten most populated cities in the United States.

C.
Yosemite National Park, in central California, covers nearly 1,200 miles of mountainous terrain.

D.
The state of California is also called the Golden State.