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简述利用血球计数板定量微藻的操作方法及注意事项。

答案

参考答案：

操作方法：①低倍镜下，调整焦距看清计数板划线部分。②清洗计数板，晾干，平放桌上，盖好盖玻片。③充分摇匀计数藻液样品，迅速取样。④把吸管口放到计数板上的盖玻片边缘处，轻压橡皮头使藻液自行流入计数板内，静至2-3分钟。⑤计数对角两大格，取平均值。

注意事项：①取样前，藻液样品要保证充分摇匀。②藻液流入计数板内时，不能流出或有空泡③避免重复计数。④样品浓度太大要稀释

单项选择题

The common cold is the world’s most widespread illness, which is plagues that flesh receives.
The most widespread mistake of all is that colds are caused by cold. They are not. They are caused by viruses passing on from person to person. You catch a cold by coming into contact, directly or indirectly, with someone who already has one. If cold causes colds, it would be reasonable to expect the Eskimos to suffer from them forever. But they do not. And in isolated Arctic regions explorers have reported being free from colds until coming into contact again with infected people from the outside world by way of packages and mail dropped from airplanes.
During the First World War soldiers who spent long periods in the trenches, cold and wet, showed no increased tendency to catch colds.
In the Second World War prisoners at the notorious Auschwitz concentration camp, naked and starving, were astonished to find that they seldom had colds.
At the Common Cold Research Unit in England, volunteers took part in Experiments in which they gave themselves to the discomforts of being cold and wet for long stretches of time. After taking hot baths, they put on bathing suits, allowed themselves to be with cold water, and then stood about dripping wet in drafty room. Some wore wet socks all day while others exercised in the rain until close to exhaustion. Not one of the volunteers came down with a cold unless a cold virus was actually dropped in his nose.
If, then, cold and wet have nothing to do with catching colds, why are they more frequent in the winter Despite the most pains—taking research, no one has yet found the answer. One explanation offered by scientists is that people tend to stay together indoors more in cold weather than at other times, and this makes it easier for cold viruses to be passed on.
No one has yet found a cure for the cold. There are drugs and pain suppressors such as aspirin, but all they do is to relieve the symptoms.

Arctic explorers may catch colds when ______.

A. they are working in the isolated Arctic regions
B. they are writing reports in terribly cold weather
C. they are free from work in the isolated Arctic regions
D. they are coming into touch again with the outside world
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单项选择题

发票内容填写错误，不应该涂改后继续使用或销毁，应另开具发票，并在误填的发票上注明“（）”四个字。

A.涂改作废

B.误填作废

C.继续使用

D.误填销毁
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