12. ambiguous: adj.

①having more than one possible meaning 有不止一种意思的;有歧义

②uncertain in meaning or intention.意向不明的；暧昧的

ambiguously 　adv. 　ambiguousness 　n.

11. aluminium: chemical element; a light silvery metal. 铝。

10. altitude. n.① height above sea-level 海拔，高度.eg :What is the altitude of the village?

② 常作复数，海拔甚高的地方。eg: It is difficult to breathe at these altitude.

在这些高的地方很难呼吸。

9. alternative. adj 作定语。可用以代替其他事物的；另一可选用的；其他的。

　Have you got an alternative suggestion?你有没有其他的建议？

8. algerbra. n .[u]. 代数学，代数。

7. alcoholic, adj ①酒精的；含酒精的；②由喝酒引起的。

6. advocate. v. speak publicly in favor of sth; recommend ; support. 拥护；提倡；主张。eg: Do you advocate banning cars in the city centers? 你支持禁止汽车在市中心通行这一主张吗？ 　　advocacy. n .

5. adolescent adj 青春期的；青春期特有的。adolescence. n.

4. abundant. adj　　 ① more than enough ;plentiful.丰富的，充裕的

We have abundant proof of his guilt

② 作表语 ，富有某事物- in sth :having plenty of sth; rich insth。

3. absurd. adj ①unreasonable; not sensible. 不合理的；荒唐的；谎谬的

eg: What an absurd suggestion! 多么荒唐的建议

② foolish in a funny way. 愚蠢的；怪诞不经的

eg: That uniform makes them look absurd. 他们穿着那种制服看起来怪模怪样的。