注视打开的电灯几分钟后闭上眼睛，眼前会产生一片黑背景，黑背景_爱下问搜题

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问题多项选择题

注视打开的电灯几分钟后闭上眼睛，眼前会产生一片黑背景，黑背景中间有一电灯形式的光亮形状，这就是（）

A．后像

B．继时对比

C．正后像

D．无彩色对比

答案

参考答案：A, C

完形填空

完形填空（共20小题，每小题1分，满分20分）
I made up my mind to drive to South Carolina to meet my friends in my used car. Though I had only been there once 1 and did not know the 2 very well. I was on the 3 after I had made some inquiries (询问).
At Ashvelle, there was a crossroad where I could go on along the main road or I could take a short cut. The short cut was to 4 several hills and was dangerous ,I hesitated

(犹豫)for a little while and then chose the main road, for I wanted to be 5 .
Something strange happened after I drove a long 6 and found it was not the correct road that I wanted to 7, but the hilly road I decided to avoid .I realized that it was at the 8 that I had made the 9 mistake. “What shall I do?” I asked myself .If I went back to take that road again, it would be very late by the time I got to Co

lumbia. Thin it 10 , I decided to go on. “If 11 people can go along this road, why can’t I?” I 12 myself
The short cut, to my surprise ,was not that 13 .In fact, it was only a very peaceful country road, 14 up and down two low 15 .There was 16 traffic. On both sides of the road, you could see trees, wild flowers, and 17 with cows and horses. My fear was 18 with the wind. Listening to the beautiful country music over my car stereo (立体声), I drove on and 19 the scenery which was so quiet and so natural .Even my used car forgot to give me 20 .It was just in this light heartedness that I arrived at my destination. My friends, after they heard what had happened to me, all said it sounded like an adventure.

C．disappointed

D．interesting

单项选择题

通过管道、加压泵站、水塔、高位水池等配水设施将满足一定水压要求的水量分配到用户是( )的任务。

A．取水工程
B．净水工程
C．配水工程
D．输水工程