题目内容：
根据以下资料，回答题：Directions: The following is a passage about environment．After reading it, you are required to complete the outline below it ( No．46 to No．50 ). You should write your answers briefly ( in no more than three words ) on the Answer Sheet correspondingly.
Environment is everything that surrounds us: plants, animals, buildings, country, air, water--in fact eve-
rything that can affect us in any way．And environment differs in different parts of the world.
Ecology is the science of how living creatures and plants exist together and depend on each other on the local environment Where an environment is undisturbed, the ecology of an area is in balance．But if a creature dies out or an alien (相异的)species is introduced, then the ecology of this area will be upset.
Man is a part of the environment and has done more to upset the ecology during his short span on earth than any other living creature．He has poisoned the atmosphere and polluted both land and water．He has wasted the earth' s natural resources with no thought for the future．He has killed a lot of precious animals for his delicacies(精美食品)on the table and for his elegant overcoats.
Since man has done so much damage, it is up to man to try to put matters right．And the sooner he does
something about it, the better.
46______________ is everything that surrounds us.
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