雷电对地放电过程中的主放电阶段持续时间在（）范围内。 A.50~00μs B.500 发布时间：2018-02-14 21:27 │ 来源：www.tikuol.com 题型：单项选择题 问题： 雷电对地放电过程中的主放电阶段持续时间在（）范围内。A.50~00μsB.500~1000μsC.10~20msD.50~00ms
题型：单项选择题 完形填空。 Mary is 1 American school girl. She is now in Beijing 2 her parents. Mary doesn't know Chinese, 3 she likes learning Chinese. She often 4 Chinese to her Chinese friends, usually they 5 understand her because she 6 Chinese 7 . It's Sunday morning, She goes out. She 8 in the street. She is going to the zoo to see elephants and monkeys, but she doesn't know how to 9 . She asks a Chinese boy. The boy can't understand her. Then she takes out a pen and a piece of paper. She draws an elephant 10 it, and shows the picture to the boy. The boy understands now, then shows Mary the way to the zoo. ( )1. A. a ( )2. A. at ( )3. A. but ( )4. A. speaks ( )5. A. aren’t ( )6. A. can speak ( )7. A. good ( )8. A. is walking ( )9. A. get to there ( )10. A. on B. × B. with B. or B. tells B. don‘t B. isn’t speak B. well B. walk B. gets there B. in C. another C. for C. and C. says C. are C. can’t speak C. fine C. walking C. getting to there C. at D. an D. and D. so D. talks D. doesn’t D. are speaks D. nice D. are walking D. get there D. with 查看答案