产权清晰实际上是指产权在经济上的清晰。()
参考答案:错
—Is Jack on duty today? —It ______ be him. It is his turn tomorrow.
A.mustn’t
B.won’t
C.can’t
D.needn’t
—Lily,______ do you study for a math best? —By asking my teacher for help.
A.how
B.who
C.why
D.what