下列对实验现象的描述不正确的是

A．把洁净的铜丝放入硝酸银溶液中，溶液由无色逐渐变蓝色

B．加热饱和石灰水，出现白色浑浊

C．硫在氧气中燃烧产生蓝紫色火焰，生成无色无味的气体

D．在氨水中滴加几滴石蕊溶液，溶液呈蓝色

In the following essay,each blank has four choices．Choose the best answer and writedown on the answer sheet．
Communicating via E—mail is by far the most common Internet activity．You can (71) with anyone in the world who has an Internet address or E—mail (72) with a systemconnection to the Intemet．All you need is (73) the Internet and an E—mail program．Two ofthe most widely used E．mail programs are Microsoft’s (74) and Netscape’S Navigator．Atypical E．mail message has three basic (75) ：header，message，and signature·

A．attach with
B．grasp
C．possess
D．access to