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问题 选择题

当今世界三大环境问题是酸雨、臭氧层空洞和温室效应，其中形成酸雨的主要原因是人们向空气中大量排放了有害气体，它们主要是

A．CH4和CO

B．SO2和CO

C．CO和CO2

D．SO2和NO2

答案

答案：D

题目分析：形成酸雨的污染物主要是二氧化硫和氮的氧化物。

点评：二氧化硫形成酸雨的原理主要是二氧化硫与水形成亚硫酸、亚硫酸被氧化形成硫酸；氮的氧化物形成硝酸型酸雨。

单项选择题

胰腺最常见的肿瘤是（）。

A.腺癌

B.假性囊肿

C.胰岛细胞瘤

D.囊腺癌
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单项选择题

Sometimes we have specific problems with our mother; sometimes, life with her can just be hard work. If there are difficulties in your (1) , it’s best to deal with them, (2) remember that any (3) should be done (4) person or by letter. The telephone is not a good (5) because it is too easy (6) either side to (7) the conversation.

Explain to her (8) you find difficult in your relationship and then (9) some new arrangements that you think would establish a (10) balance between you. Sometimes we hold (11) from establishing such boundaries because we are afraid that doing (12) implies we are (13) her. We need to remember that being (14) from our mother does not (15) mean that we no longer love her. If the conflict is (16) and you cannot find a way to (17) it, you might decide to give up your relationship with your mother for a while. Some of my patients had (18) "trial separations". The (19) allowed things to simmer down, enabling (20) .

（12）（）

A.it

B.which

C.what

D.so
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