20世纪60年代，美国总统肯尼迪问起“危机”一词在汉语里怎么解释。有人告诉他说：“在汉语里，危机就是由危险和机会两个词组成，即危险意味着机会。”肯尼迪听后拍案叫绝：“中华文化能把两个毫不相干的词融化成一个东西，太伟大了！”这里说中华文化的伟大，主要是指中华文化蕴涵着丰富的[ ]

A、哲学思想

B、唯物论思想

C、辩证法思想

D、时代精髓

We have already covered the topic of network addresses. The first  (1) in a block (in classes A, B, and C) defines the network address. In classes A, B, and C,if the hostid is all ls,the address is called a direct broadcast address. It is used by a(2) to send a packet to all hosts in a specific network. All hosts will accept a packet having this type of destination address. Note that this address can be used only as a (3) address in an IP packet. Note also that this special address also reduces the number of available hostid for each netid in classes A,B，and C． In classes A, B, and C, an address with all ls for the netid and hostid (32bits) define a (4) address in the current network.A host that wants to send a message to every other host can use this address as a destination address in an IP packet. However, a router will block a packet having this type of address to confine the broadcasting to the (5) network. Note that this address belongs to class E.

空白（4）处应选择（）

A.unicast

B.multicast

C.broadcast

D.anycast