动物实验中要求坚持的“3R”原则不包括（） A.ReDuCtion（减少） B.Re

等腰三角形的一个内角是70°，则这个等腰三角形的底角是______．

阅读理解。

     Do you ever find yourself getting really angry for almost no reason? Or suddenly feeling down

without knowing why? Going from sadness to anger to joy in a matter of minutes can make many

teens feel as though they're losing their control. But why is the feeling of being on an emotional roller

coaster (急转突变) so common among teens?

     Dealing with constant change and pressure is part of the answer. Maybe you're starting a new

school and not able to see old friends as much. Getting good grades or wanting to be better in sports

or other activities can be a concern for many teens. It might feel as though there just isn't enough time

to do everything.

     Being a teen means struggling with identity and selfimage. Being accepted by friends feels

extremely important. Teens also may notice, for the first time, a sense of distance from parents and

family. You may feel you want to be on your own and make your own decisions, but it can also

seem overwhelming (压倒的) and even a bit lonely at times. As fun and exciting as this time is, it also

can be a time of confusion and conflict.

     Another important cause for mood swings is biology. When puberty (青春期) begins, the body

starts producing sex hormones. These hormones cause physical changes in the body. But in some

people, they also seem to cause emotional changes-the ups and downs that sometimes feel out of

control.

     Feeling irritable or shorttempered can be signs of depression.  So can feelings of boredom or

hopelessness. Many people think of depression as feeling sad, but depression can also bring feelings

of moodiness, impatience, anger. When depression gets in the way of enjoying life or dealing with

others, that's a sign you need to do something about it, like talking to a counselor or therapist (治疗

专家) who can help you deal with it.

     Here are some things you can do that might make those bad moods a bit easier to handle: recognize

you're not alone, catch your breath, count to 10, talk to people you trust, exercise, cry or wait.

 1. From the passage, we can infer that the teens' emotional changes are ________.

A. abnormal                          

B. reasonable

C. predictable                        

D. natural

2. How many reasons does the author refer to in the passage for children's emotional changes? 

A. Two.                              

B. Three.

C. Four.                              

D. Five.

3. What does the passage mainly talk about?

A. Why people are in bad mood.

B. What the result of depression is.

C. Bad mood can cause bad effects.

D. It's important to be dependent.

4. What does the underlined word "irritable" in the fifth paragraph mean?

A. Upset.                            

B. Angry.

C. Unhappy.                          

D. Impatient.

下列哪项不是急性毒性试验动物选择的原则（）。

A.选择急性毒性反应与人近似的实验动物

B.选择易于饲养的实验动物

C.选择繁殖生育能力较强的实验动物

D.选择刚断乳的实验动物

E.选择价格较低的实验动物

女性，18岁初潮，经量极少，规律，24岁结婚至今未孕，最可能的诊断是（）

A.双子宫

B.双角子宫

C.单角子宫

D.幼稚子宫

E.始基子宫

试述蒸发岩与油气聚集的关系。