(41) is a protocol that a host uses to inform a router when it joins or leaves an Internet multicast group.
(42) is an error detection code that most data communication networks use.
(43) is an interior gateway protocol that uses a distance vector algorithm to propagate routing information.
(44) is a transfer mode in which all types of information are organized into fixed form cells on an asynchronous or non-periodic basis over a range of media.
(45) is an identifier of a web page.

A．ISDN

B．X.25

C．Frame Relay

D．ATM

鼓励孩子时应该（）

A.重视孩子的努力和进步，避免与其他孩子做比较

B.对于孩子的进步，要多用具体的言辞来肯定

C.尽量少用抽象的赞美来敷衍

D.多于其他孩子比较