One ofthe main resposibilities of ICMP is to report(1).Although technology has produced increasingly relaible transmission media, errors still exist and must be handled. IP is an (2) protocol. This means that error checking and error control are not a concern of IP. ICMP was designed, in part, to compensate for this shortcoming. Howerver, ICMP does not (3) errors, it simply report them. Error correction is left to the higher-level potocols. Error messages are always sent to the original (4) because the only information available in the datagram about the route is the source and destination IP addresses. ICMP use the source IP address to sent the error massage to the source of the (5).

空白（1）处应选择（）

A.numbers

B.functions

C.strings

D.errors

枕大神经和枕小神经注射的适应证（）

A.颈椎病、颈神经根炎、颈肩臂疼痛（C4~5）

B.颈椎病、上肢神经血管疾病、幻肢痛

C.颈椎性眩晕、上颈椎段疾病及枕神经痛

D.颈椎病、颈椎退行性变、肌筋膜炎

E.肩周炎