[单项选择]Body Cells People are the most complex of all organisms._________(46). The specialized cells of the body depend upon each other for such things as nourishment and the removal of the waste matter._________(47). Or if the excreting cells did not take away poisonous waste, the cells of the body would be poisoned and die. Under a microscope, a cell looks like a bit of clear jelly with a thin wall round it._________(48 ). In every cell there is a part like a little ball. This is the nucleus, which organizes the work of the cell. Though cells were discovered two and a half centuries ago, it is only in the last hundred years that knowledge of the work of the nucleus has developed._________ (49). All cells reproduce their own kind and grow. In performing their work, cells become tired, worn-out and die. If the tissue of the organ is to maintain its health, new cells are required to replace the old ones. The healthy cells accomplish this by splitting their bodies so that one cell

[单项选择]Body Cells People are the most complex of all organisms._________(46). The specialized cells of the body depend upon each other for such things as nourishment and the removal of the waste matter._________(47). Or if the excreting cells did not take away poisonous waste, the cells of the body would be poisoned and die. Under a microscope, a cell looks like a bit of clear jelly with a thin wall round it._________(48 ). In every cell there is a part like a little ball. This is the nucleus, which organizes the work of the cell. Though cells were discovered two and a half centuries ago, it is only in the last hundred years that knowledge of the work of the nucleus has developed._________ (49). All cells reproduce their own kind and grow. In performing their work, cells become tired, worn-out and die. If the tissue of the organ is to maintain its health, new cells are required to replace the old ones. The healthy cells accomplish this by splitting their bodies so that one cell

[判断题]Fat cells block body heat from escaping quickly.

[单项选择] Scratchy throats, stuffy noses and body aches all spell misery, but being able to tell if the cause is a cold or flu may make a difference in how long the misery lasts. The American Lung Association (ALA) has issued new guidelines on combating colds and the flu, and one of the keys is being able to quickly tell the two apart, That’’ s because the prescription drugs available for the flu need to be taken soon after the illness sets in. As for colds, the sooner a person starts taking over-the-counter remedy, the sooner relief will come. The common cold and the flu are both caused by viruses. More than 200 viruses can cause cold symptoms, while the flu is caused by three viruses--flu A, B and C. There is no cure for either illness, but the flu can be prevented by the flu vaccine, which is, for most people, the best way to fight the flu, according to the ALA. But if the flu does strike, quick action can help. Although the flu and common cold have many similarities, there am
A. one should identify the virus which causes it
B. one should consult a doctor as soon as possible
C. one should take medicine upon catching the disease
D. one should remain alert when the disease is spreading