有如下程序： #include ＜iostream＞ using namespace std： class A{ public： virtual void funcl( ){cout＜＜"A1"；} void func2( ){cout＜＜"A2"；} }； class B：public A{ public： void funcl( ){cout＜＜"B1"；} void fllnc2( ){cout＜＜"B2"；} }； int main( ){ A*p=new B； p-＞funcl( )； p-＞func2( )； return 0： } 运行程序，屏幕上将显示输出

A．B182

B．A1A2

C．BlA2

D．AlB2

In low-speed network，it is usually adequate to wait for congestion to occur and then react to it bytelling the source of packets to slow down．In high-speed networks，this approach often works poorly，because in the (71) between sending the notification and notification arriving at the source，thousands of additional (72) may arrive．In ATM network，a major tool for preventing (73) is (74) control．When a host wants a new virtual (75) ，it must describe the traffic to be offeredand the service expected．

（72）处填（）。

A．packets

B．cells

C．message

D．files