Which Best Describes the Effects of the Massive American and British

Which best describes the effects of the massive American and British aerial bombardment of Germany?

A) It was effective at first,until the Germans developed effective defenses.
B) It had little effect until fighters were used to protect the bombers.
C) It had little direct effect on the war,but the bombing undermined German morale severely.
D) In all its aspects,the bombardment was a great success.