心理、生理性危险、危害因素主要包括什么？

等比数列{a_n}中，S_n是其前n项和，S₄=1，S₈=3，则a₁₇+a₁₈+a₁₉+a₂₀=______．

各大洲中面积最大，跨纬度最广，东西距离最长的是亚洲。[ ]

女，16岁，生气后未进早餐即去上学，学习写字3小时后突然出现右手间歇性抽搐并伴有感觉异常，继之抽搐，由肢体远端扩散至近端，意识尚清，既往有类似发作病史2年。

最可能的诊断是（）

A.低血糖抽搐

B.癔病发作

C.癫痫大发作

D.癫痫局限性发作

E.电解质紊乱

Here are a few tips we’ve put together to help you learn English well.

Speak, speak, speak

Practise speaking as often as you can—even speaking to yourself is good practice.

Try recording yourself whenever you can. Compare your pronunciation with the master version, see how you can do better and have another go. If you do this several times, you will find that each version is better than the last.

Why not learn with someone else?

It helps if you can learn with someone else. If you can persuade a friend or a family member to study with you, it will make you keep working.

Don’t get stuck by a word you don’t know.

Practise improvising（即兴的）ways of getting your meaning across when speaking spontaneously（本能地）, even if you don’t know the exact words or phrases. Think of things you might want to say whenever you have spare time. Use facial expressions, hand movements, anything to get your meaning across.

Language learning is also about intuition（直觉）.

Guesswork is an important way to learn a new language. When listening to recorded material, you aren’t expected to understand everything first round. If you play the same piece several times, you will most probably understand something new each time.

Build up your vocabulary.

A wide vocabulary is the key to successful language learning but don’t try to learn too much at once. It’s best to study frequently, for short periods of time. Take at most six or seven items of vocabulary and learn them. Put them into sentences to fix them in your mind, then come back to them later.

And above all, have fun!

小题1:Why should one have himself recorded when practicing speaking?

A．To improve his speaking.

B．To record his own progress.

C．To encourage others to start.

D．To compare himself with others.小题2:In the writer’s opinion, which of the following is the most important in leaning English?

A．Speaking.

B．Pleasure.

C．Intuition.

D．Vocabulary.小题3:It is implied in the passage that _______ is helpful when you are learning English.

A．body language

B．a good material

C．a good friend

D．a proper dictionary小题4: According to the passage, one should ______ when you are learning English.

A．always work with other people

B．be able to guess everything new

C．often review what he has learnt

D．take little notice of grammar

压缩机系统开车前油箱液位必须达到（）

A.95%；

B.30%；

C.50%；

D.70%。