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问题 选择题
已知椭圆C：
x2
4
+y2=1的焦点为F1，F2，若点P在椭圆上，且满足|PO|2=|PF1|•|PF2|（其中为坐标原点），则称点P为“★点”，那么下列结论正确的是（　　）
A．．椭圆上的所有点都是“★点”
B．．椭圆上仅有有限个点是“★点”
C．．椭圆上的所有点都不是“★点”
D．．椭圆上有无穷多个点（但不是所有的点）是“★点”
答案

设椭圆上的点P（x0，y0），|PF1|=2-ex0，|PF2|=2+ex0，因为|PO|2=|PF1|•|PF2|，则有4-e2

x20
=
x20
+
y20
=
3
4
x20
+1，解得x0=±
2
，因此满足条件的有四个点，

故选B．

多选题

关于声音，下列说法中正确的是 [ ]

A．声波具有能量　　

B．声音不能在真空中传播　

C．“禁鸣喇叭”是在传播途中控制噪声　　

D．只要物体在振动，我们就一定能听到声音

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完形填空

Directions: Complete the following passage by filling in each blank with one word that best fits the context.

Job hunting has always been a headache for college graduates. Though many graduates are employed right after graduation, some are   48 . Most serious of all, some still have no idea  49    to go working even a long time after graduation.

The reasons   50  this phenomenon are various. On the one hand, a few years ago colleges and universities enrolled so many students in popular majors, such as economy, finance and so on   51    the number of graduates is greater than the need in the market. On the other hand, most graduates would rather stay in large cities without suitable jobs to do   52  go to the country.

I believe the problem can be solved   53  both colleges and students take measures. First, they should research the market and develop special skills to suit   54  needs. Second, students’ attitude towards employment should be changed. They should go to some   55  cities and the countryside. There they can also give full play to their professional knowledge. In a word, if we pay much attention, the problem can be solved.
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