以下程序的输出是( ) class Base { int a; public: Base(int sa):a(sa){cout<<"a="<
<<"构造Base"<
A.
a=1构造Base b=2构造Base2 c=3构造Base3 d=4构造Myclass
B.
a=4构造Base b=3构造Base2 c=2构造Base3 d=1构造Myclass
C.
a=1构造Base b=2构造Base2 a=1构造Base c=3构造Base3 d=4构造Myclass
D.
a=4构造Base b=3构造Base2 a=4构造Base c=2构造Base3 d=1构造Myclass