One ofthe main resposibilities ofICMP is to report  （） . Although technology hasproduced increasingly relaible transmission media, errors still exist and must be handled. IP isan  （）  protocol. This means that error checking and error control are not a concem ofIP. ICMP was designed, in part, to compensate for this shortcoming. Howerver, ICMP doesnot  （） errors, it simply report them. Error correction is left to the higher-levelpotocols. Error messages are always sent to the original  （）  because the only informationavailable in the datagram about the route is the source and destination IP addresses. ICMP usethe source IP address to sent the error massage to the source ofthe（）.

One ofthe main resposibilities ofICMP is to report（）

A．numbers

B．functions

C．strings

D．errors

折扣定价是指（）。

A、对基本价格作出让步，直接或间接降低价格

B、对基本价格作出一定的让步，直接降低价格

C、对基本价格作出一定的让步，直接或间接降低价格

D、对现有价格作出一定的让步，直接或间接降低价格