When you think of the Internet, you probably think of ".com." Just what do those three letters at the end of a World Wide Web address mean Every computer that hosts data on the Internet has a (71) numerical address. For example, the numerical address for the White House is 198.137.240.100. But since (72) people want to remember long strings of numbers, the (73) was developed. It is a critical part of the Internet’s technical infrastructure, correlates a numerical address to a word. To (74) the White House website, you could type its numerical address into the address box of your web browser. But most people prefer to use "www. whitehouse. gov." In this case, the domain name is (75) .

（75）处填（）。

A．www.

B．www. whitehouse

C．www. whitehouse. gov

D．whitehouse. gov

甲地和乙地相距500公里时，如果在1厘米等于50公里比例表的地图上，这两地之间的距离是多少厘米？（）

A．5

B．10

C．15

D．100