Entry Word: exhaust

Function: verb

Definition 1: to use up all the physical energy of [The long day at the county fair had exhausted everyone.]
Synonyms burn out, do in, drain, fatigue, tire, tucker (out), wash out, wear, wear out, weary
Related Words debilitate, enervate, enfeeble, sap, waste, weaken
Phrases wear to a frazzle
Near Antonyms activate, energize, invigorate, strengthen, vitalize; relax, rest, unwind

Definition 2: to make complete use of—[We had only been at the theme park for barely two hours and were on the verge of exhausting our spending money.] see DEPLETE

What could you use as a synonym for the word exhaust in the following sentence?

Maurice and Steve had been walking all day and were exhausted.
A.
strengthened
B.
activated
C.
drained
D.
unwinding

C. drained