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（3）处应选择（）

A.correct

B.conduct

C.product

D.connect

寄生虫感染时，浸润的炎症细胞主要是

A．嗜中性粒细胞

B．单核细胞

C．淋巴细胞

D．嗜酸性粒细胞

E．浆细胞