题干

在各图中,根据已给出的入(出)射光线及透镜的类型,分别画出它们的出(入)射光线.

上一题 下一题 0.0难度 选择题 更新时间:2019-10-18 03:08:23

答案(点此获取答案解析)

解:如图所示:

同类题1

根据下表中烃的分子式排列规律,判断空格中烃的同分异构体数目是
1
2
3
4
5
6
7
8
CH4
C2H4
C3H8
C4H8
 
C6H12
C7H16
C8H16

同类题5

阅读理解

    My transportation was unexpectedly smooth and I arrived at the meeting half an hour earlier. I kept my eyes on the restaurant door. Several customers entered, but not my friend. At 6:00 pm, she sent me a text message:“Urgent work to finish. Will be 20 minutes late.”

I had left my book in the office, so I spent the time thinking of my experiences of being late in China. On my first visit in 1985, punctuality was deeply rooted in the Chinese hearts. There were no traffic jams then.

    As a teacher in Canada, I always insisted on punctuality. I would open the classroom door to a late student for the first time and the second, but not the third. During the six years I worked for CCTV, I had a Chinese friend whom I often saw at lunch time, or after work. We used to meet at the subway station nearby. He was always late by 10-20 minutes. To myquestion, “You were busy?” he would surprisingly answer, “ No.” Once I asked him to check the clock in his office, he smiled.

    In March 2015, I got permanent residence (居住权) in China.The ceremony was scheduled for 9:00 am at the Public Security Bureau on the Second Ring Road. I told my driver I had to get there by 8: 40 am. “No problem,”he replied. But he thought he had time to drop someone off at the airport before picking me up. I desperately waited for him. Then, to rub salt into my wound, he had to stop at the exit of a gas station. Finally, I entered the room at 9:07 am ── the last guest to arrive!