简述Maxam-Gilert化学降解法测DNA序列的原理。

Reading comprehension.

     People in different countries have different ways of doing things. Something that is polite in one country

may be quite impolite in another. In Britain, you mustn't lift your bowl to your mouth when you are having

some liquid (液体) food. But it's different in China. And in Japan you even needn't worry about making much

noise when you have in. It shows that you are enjoying it. But it is considered as bad manners in Britain. If

you are a visitor in Mongolia, what manners do they wish you to have? They wish you to give a loud "burp"

(打嗝) after you finish eating. Burping shows that you like the food.

     In Britain, you should try not to put your hands on the table when you're having a meal. In Mexico,

however, guests are expected to keep their hands on the table during a meal. But in Arab countries you must

be very careful with your hands. You mustn't eat with your left hand. Arabs consider it very bad manners

eating with left hands. So, what should you do if you are on a visit to another country? Well, remember when

in Rome do as the Romans do. You can ask the local people to help you or just watch carefully and follow

them.

Fill in each blank according to the passage you read. One word only for each blank.

     Different countries have different table manners, In Britain, you should remember not 1              lift your

bowl to your mouth when you are having some liquid food. And you should try not to put your hands on the

table when 2              a meal. If you are visiting Mongolia, you are supposed to give a loud "burp" after you

finish eating. Burping shows that you enjoy the food. In Arab countries you must be very careful with your

hands. Eating with your left hand is considered to 3               bad manners. So, if you are visiting another

country, remember to do as the 4               people do. You can ask them for 5               or just watch

carefully and follow them.

老奶奶在选购瓷碗时，总爱用轻轻敲打瓷碗，仔细听声的方式进行比较，以此来判断瓷碗是否有不易观察到的裂纹。这种辨别方法依据的是声音的音色和_____________

简述我国基础教育课程改革的理念。

（）又被称为心理感冒。

A、抑郁

B、沮丧

C、悲哀

D、郁闷