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问题 选择题
已知椭圆
x2
a2
+
y2
b2
=1(a＞b＞0)的一个焦点是圆x2+y2-6x+8=0的圆心，且短轴长为8，则椭圆的左顶点为（　　）
A．（-3，0）B．（-4，0）C．（-10，0）D．（-5，0）
答案

∵圆x2+y2-6x+8=0的圆心为（3，0），

∴椭圆

x2
a2
+
y2
b2
=1(a＞b＞0)的一个焦点为F（3，0），得c=3

又∵短轴长为2b=8，得b=4

∴a=

b2+c2
=5，可得椭圆的左顶点为（-5，0）

故选D

完形填空

根据语篇情景，用恰当的短语或句子填空，使之意思完整。（每空2分，共6分）

After college when I moved to London, I was surprised at how polite everyone was in the subways. I was more touched when I traveled to Japan. In both places, people tried to (    小题1:  ). On moving stairs, everyone stood to the right and walked on the left. On elevater, everyone would stand over to the side and allow others to go out before they would begin to enter.

So, that is a polite social behavior: When we have to go up escalator, we will ( 小题2: ). That will give others who are in a hurry a choice of walking up the left-hand side of the escalator. When we are going to enter a elevater, the subway, or a doorway, we will wait for others to exit(离开) before (  小题3:   ).
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