Question

is a clause?When World War II broke out, Beardenserved in the U.S. Army.A broke outB in the U.S. ArmyC served in the U.S. ArmyD When World War II broke out

Answer 1

I'm pretty sure it is D: "When World War II broke out"
It is a subordinating (dependant) clause.

A is a predicator
B is a prepositional phrase
C is a predicate

I'm pretty sure, but if I have got anything wrong, I'd be happy to be corrected.

Answer 2

It is D. When World War II broke out

Because it contains a subject and a predicate. The subject is "Bearden" and the predicate is "served".