______ (任何怀疑他能力的人) needs only to look at his contribution to the company over the past year.

A．Because they get low grades.
B．Because they exhaust the reference sources in the library.
C．Because they can spend only limited time with the professors.
D．Because their teachers do not grade every assignment of them.

A．a single currency may not be suitable to all its member countries
B．a political alliance is better than an economic union
C．the prices in the member countries will decline
D．the purchasing power of consumers in the member countries will decline