Which of the following sentences from the passage has a dependent clause underlined?

A. I tipped my head back and closed my eyes, breathing in the air.
B. Weeks had already come and gone without a break from the vicious sun.
C. Within the hour, the whisper had grown to a roar.
D. If I wait long enough, relief will come, just like the rain!

D. If I wait long enough, relief will come, just like the rain!