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问题 选择题

如图所示的曲线为一质点在恒定合外力作用下运动的一段轨迹，质点由A到B的时间与质点由B到C的时间相等，已知曲线段长度大于段长度，则下列判断正确的是（   ）

A．该质点做非匀变速运动

B．该质点在这段时间内可能做加速运动

C．两段时间内该质点的速度变化量相等

D．两段时间内该质点的速度变化量不等

答案

答案：C

题目分析：质点在恒力作用下运动，加速度恒定，时间相等，速度变化量相等，D正确。

完形填空

基础训练篇（16）

We must have water to live. __ 1________the water we use is clean and fresh, it will make us ill. The animals __ 2________ (live) in and around lakes and rivers must also have clean water. Our rivers and lakes supply most of our water. The clear, blue water found by the first American settlers has changed. Many of our water sources are now __ 3________. They are filled __ 4________ dirt and waste which cannot be cleaned out. In many places, water is not safe for us to use.

Lake Erie was __ 5________ a beautiful lake. Now it has been called “a dying lake”. Waste from nearby homes and factories has been dumped into __ 6________. Fish can no longer live in much of its polluted water. George Washington once called the Potomac “__ 7________ finest river in the world”. Now its water is no longer blue. Instead, it is soupy green. Suds(肥皂泡沫), from detergents（洗涤剂；洗衣粉） used to wash clothes, often cover the water of our rivers.

Water cannot __8___________(make) in a factory. Once water is polluted, it is __ 9________ to make it clean and safe again. We must learn to take care of the water __ 10_______ we now have.
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单项选择题

后凯恩斯主流学派把滞胀因归结为（）。

A、需求拉上型通货膨胀和周期性失业

B、成本拉上型通货膨胀和周期性失业

C、成本推动型通货膨胀和结构失业

D、结构性通货膨胀和结构性失业
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