When blood is sent to the lungs by the heart, it has come back from the cells in the rest of the body. So the blood that goes into the wall of an air sac (Jl) contains much dissolved carbon dioxide bu...
In the early days of nuclear power, the United States make money on it. But today opponents (反对者) have so complicated its development that no nuclear plants have been ordered or built here in 12...
As the 11 of life continues to increase, we are fast losing the art of relaxation. Once you are in habit of rushing through life, being on the go from morning till night, it is hard to slow down. But ...
Most young people enjoy some form of physical activity. It may be walking, cycling or swimming, or in winter, skating or skiing. It may be a game of some kind—football, hockey, golf, or tennis. ...
The English policeman has several nicknames ( 绰号 ) but the most frequently used are "copper" and "bobby". The first name comes from the verb "to cop " (which is also ...
Personality is, to a large extent, inherent—A-type parents, usually bring about A-type children. But the environment must also have a 11 effect, wince if competition is important to the parents ...
When we analyze the salt salinity(盐浓度) of ocean waters, we find that it varies only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic p...
At the close of each business day, most trained teachers, administrators, politicians, and statesmen make objective analyses of all that has transpired. They then carefully evaluate performance in the...
In the United States, it is not 11 to telephone someone very early in the morning. If you telephone him early in the day, while he is shaving or having breakfast, the time of the call shows that the m...
Scientists at Sussex University appear to be on the way to 11 how the mosquito, carrier of diseases such as malaria and yellow fever, homes in on its target. The problem is that they have found that t...