Often, the fact ________ unemployed people get help from government ________ this from happening, but not always.

A．how, to prevent

B．that, prevents

C． how, preventing

D．why, prevented

下列函数中对调用它的函数没有起到任何作用的是( )。

A．void f1(double &x)--x;

B．double f2(double x)return x-1.5;

C．void f3(double x)--x;

D．double f4(double*x)--*x;return*x;