设f(x)=ke-|x|(-∞＜x＜+∞)是一概率密度，则k=______．

A. The war was rapidly reflected in American literature.
B. The war was hardly reflected in American literature.
C. Hemingway was the only author to write about the war.
D. American literature was slow to reflect the war.

A. He does not know who Alice is.
B. He has found a job as a messenger.
C. He does not want to deliver the note.
D. He does not know where Alice is.

A. 对
B. 错