单项选择题

有如下类定义: class Test { public:    Test(){a=0;c=0;} //①    int f(int a)const {this->a=a;} //②    static int g(){return a;} //③    void h(int b){Test::b=b;}; //④  private: int a; static int b; const int c; }; int Test::b=0; 在标注号码的行中,能被正确编译的是

A.①
B.②
C.③
D.④