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People are the most"的相关试题:
[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