我国八级地震发生的间隔大概（）。A、10年B、15年C、20年D、25年

PSA吸附器的吹扫，一般使用的介质是（）。

A．氮气

B．变换气

C．空气

D．水蒸气

奶牛，2.5岁，产后已经18h，仍表现弓背和努责，时有污红色带异味液体自阴门流出。治疗原则为（）

A.增加营养和运动量

B.剥离胎衣，增加营养

C.抗菌消炎和增加运动量

D.促进子宫收缩和抗菌消炎

E.促进子宫收缩和增加运动量

Are you nervous about climbing because you think it’s too dangerous? Do you feel you’re not fit enough to climb? Do you know how to start climbing?

Let’s consider the idea that climbing is dangerous. Being afraid is natural, but if you use suitable ropes and other climbing equipments you will feel completely safe. Climbers are usually very careful because they know what they are doing is dangerous. Accidents happen, but when they do, they tend to attract a lot of publicity. As a result, people think there are many more accidents than there are in reality.

You cannot expect to start climbing straight away. Climbing is a challenge and challenges take time. It is necessary first of all that you achieve a good level of fitness. Begin as soon as you become interested in climbing—go to the gym, go swimming, take up jogging and continue to do so throughout your training period.

Discover as much as you can about climbing. Visit the library and find books especially for beginners or buy climbing magazines and look for articles which describe your situation. Look up information on the Internet. Find out about equipment, methods and places to go.

Next, take a course on a climbing wall. There are plenty of climbing walls all over the country which have trained and qualified people as instructors. Call your local leisure centre to find out if there is one in your area. These training sessions are a quick way to get experience and you are likely to meet other beginners. After this, you can do an outside course or join a club where you can meet climbers of all abilities and eventually join in group-climbing events.

At first you may not understand the importance of a good training period, but after you have completed your first climb and you are standing safely at the top of a rock feeling thrilled, then you will know it was the right thing to do.

小题1:The article is written by ______.

A．a doctor

B．an experienced climber

C．a beginner

D．a fitness instructor小题2:The writer thinks a new climber should ______.

A．begin by becoming fit

B．be aware of the causes of the accidents

C．have the courage to meet the challenges

D．do enough sports to get interested in climbing小题3:By climbing walls you can ______.

A．join a club you like

B．become qualified instructors

C．gain controlled experience

D．take part in group-climbing events小题4:The underlined word “it” in the last paragraph probably means ______.

A．the climb

B．the training

C．the equipment

D．the achievement

物象在低倍镜（5×）下清晰可见，换高倍镜（45×）后看不见了，这是因为（）

A.玻片放反了

B.高倍物镜故障

C.物象不在视野正中央

D.焦距没调好

被保护对象风险评估是安全防范领域新兴的一项工作内容，是提高安全防范系统成本/效益的一个（）。

A.必要手段

B.必要环节

C.技术要求

D.必然结果