纳米材料是粒子直径为1—100nm的材料，其研究成果已应用于医学、化工、军事等领域。纳米碳就是其中的一种，若将纳米碳均匀地分散到蒸馏水中，下列有关形成的物质的判断正确的是（  ）

①是溶液       ②是胶体   ③能产生丁达尔效应  ④能透过滤纸

⑤不能透过滤纸 ⑥静置后会析出黑色沉淀

A．①②③④

B．②③⑤⑥

C．②③④

D．②③④⑥

语法填空。

     Not all cultures greet each other the same way. Each may have its own way 1______ (express) feelings.

In Britain, people may keep 2______ certain distance and they usually do not touch 3______ (strange) as soon

as they meet. In Japan, they may bow 4______ each other when they meet. In France, people shake hands and

kiss each other twice 5______ each cheek when they meet people they know. And in South American countries,

Spain or Italy, people get close to others and are 6______ (like) to touch them. 7______ in Middle East or some

Muslim countries, men stand quite close to other men to talk; they just nod at women and seldom shake hands

with them. None of these actions is 8______ good or bad, they are simply the ways 9______ cultures have

developed. Knowing some of them can help you avoid 10______ (difficult) in communication.