_______________________________________________________________________________

Keys: 1). harmful 2). harm 3). Reading in the sun does a lot of harm to your eyes. = Reading in the sun does your eyes a lot of harm.= Reading in the sun is very harmful to your eyes.

4. exist vi. 存在；生存 existence n. 存在

[典例]

1). Does life exist on Mars? 火星上有生命吗?

2). I can hardly exist on the wage I' m getting. 我靠我挣的工资简直难以餬口。

[重点用法]

exist + prep. 存在于地方 exist on sth. 靠某物生存

[练习] 用exist的短语或其适当形式填空。

1). This plant ______ only ______ Australia.

2). Can you ______ ______ such a low salary?

3). I doubt the ______ (exist) of alien.

Keys: 1). exists; in 2). exist on to 3). existence

5. puzzle vt.&vi. (使)迷惑；(使)苦思 n.谜；难题 puzzled adj.无法了解的；困惑的 puzzling adj.令人费解的

[典例]

1). Her reply puzzled me. 她的回答把我弄糊涂了。

2). Their reason for doing it is still a puzzle to me. 他们为什麽要做此事我仍莫名其妙。

[重点用法]

sth. puzzles sb. 某事使某人迷惑/为难 sb. be puzzled by sth. 某人对......感到迷惑

puzzle about/over sth. 对某事感到迷惑或苦苦思索（以便理解） puzzle one' s brain苦思苦想；绞尽脑汁

solve a puzzle 解决一个难题

[练习] 用puzzle的适当形式填空或翻译。

1). To explain the ________ (puzzle) findings, he offers two theories.

2). I _______ (puzzle) that I haven' t heard from Liz for so long.

3). She listened with a _______ (puzzle) expression on her face.

4). No one has yet succeeded in explaining the _______ (puzzle) of how life began.

5). He _______ (puzzle) what to do next.

6). _______ _______ _______ (使我困惑的事情) is why he left the country without telling anyone.

Keys: 1). puzzling 2). am puzzled 3). puzzled 4). puzzle 5) was puzzled 6). What puzzles me

6. pull v.拉，拖，拔；移动 n.拉，拖；拉(引)力

[典例]

1). You push and I' ll pull. 你来推，我来拉。

2). I felt a pull at my sleeve and turned round. 我觉得有人扯我的袖子，便转过身来。

[重点用法]

pull ahead (of sb/sth) 领先（於某人/物） pull (sb) back（使某人）退却；撤回（某人）