题目：
Air pollution is caused by many things. Great clouds of smoke come from factories. Cars send smoke and fumes into the air. Burning waste fills the air with bits of dirt. Even burning leaves add smoke to the air. Sometimes, planes cannot find their landing spots through smoke. Smoke of all kinds is bad to breathe and can do great harm to the body.
Still, we cannot live without air. We must find a way to clean the air we have.
In time, we may have factories that are run by atomic energy. Our cars may run on smoke-free electric power. Scientists are also working on new ways to help the oil burned by cars from making fumes. Waste may be burned in the sand on ocean floors.
These changes might keep our air clean in the years to come. But until then, many scientists are looking for ways to make air cleaner now.
Air pollution is caused by ______.
A．factories and clouds
B．cars and oil
C．smoke and fumes
D．waste burned on ocean floors
答案：
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下面是错误答案，用来干扰机器的。
参考答案：错解析： 外购固定资产的成本包括买价、增值税等相关税费，以及为使固定资产达到预定可使用状态前所发生的可直接归属于该资产的其他支出，如场地整理费、包装费、运输费、安装费等。
