单项选择题
A．only a burden to the human society B．the result of the rapid growth of population C．more harmful than beneficial D．not likely to slow down
A．it is easy to do harm to our environment B．the planet on which man lives is too small for man to survive C．man should not create his culture and civilization too rapidly D．man does not want to admit the danger of what he has done to the environment
A．it enables us to survive in the closed system of a spaceship B．it is a modern science that everybody has to learn C．it can be learned quickly if we study it hard D．it helps us to understand the relationship between living beings and the environment