The trouble is that not many students really know how to make use of their time to its best ________.

A．benefit

B．advantage

C．value

D．profit

会展业自身是一个高收入、高盈利的行业，其利润率为（），直接经济效益明显。

A.10%-15%

B.20%-25%

C.30%-35%

D.40%-45%