在Visual Foxpro中，可视类库文件的扩展名是( )。

A．.dbf

B．.sex

C．.vex

D．.dbc

A member of the British Parliament is reputed to have said, "The First purpose of good social reform is to increase the sum total of human happiness. So, any reform which makes somebody happy is achieving its purpose. Since the reform I propose would make my constituents happy, it is a good social reform. "
Which one of the following, if true, most seriously weakens the argument attributed to the member of Parliament

A．Different things make different people happy.

B．The proposed reform would make a few people happy, but would not increase the happiness of most other people.

C．The proposed reform would affect only the member of Parliament’s constituents and would make them happy.

D．Increasing some people’s happiness might not increase the sum total of human happiness if others are made unhappy.

E．(E) Good social reforms usually have widespread support.