Mary is the love of my life. I still remember that I met her ____ the airport ____ a snowy evening.

A．in; at

B．at; on

C．on; by

D．to; before

有如下程序：class Base{public:int data;};class Derived1:public Base{};class Derived2:protected Base{};int main(){Derived1 d1;Derived2 d2;d1. data=0; //①d2. data=0; //②return 0;}下列关于程序编译结果的描述中，正确的是( )。

A．①②皆无编译错误

B．①有编译错误，②无编译错误

C．①无编译错误，②有编译错误

D．①②皆有编译错误