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问题 计算题

质量是2g的子弹，以200m/s的速度水平射入厚度是5cm的木板，射穿后的速度是100m/s，子弹在射穿木板的过程中所受的平均阻力是多大？

答案

600N

阅读理解
阅读理解。
                                          
     My name's Darning and I'm in Class One. I'm from China and I'm
Chinese. I'm from Beijing. Beijing is a big city. Lingling's in my class.
She's my friend.
                                           
     My name's Lingling. I'm not from England and I'm not English. I'm| Chinese. I'm in Class One. Darning is my friend. We're twelve years
old. He's from Beijing and he's in my class. We're good friends.
                                          
     My name's Wang Hui and I'm Chinese. I'm not from Beijing. I'm
from Shanghai. I'm thirteen years old. I'm in Class! One with Darning
and Lingling. They are my friends.
1. There are _____ boys. 
A. 1
B. 2
C. 3
2. Darning is from _____.
A. Jinan
B. Beijing
C. Nanjing
3. Lingling is _____ years old.
A. 10
B. 11
C. 12
4. Wang Hui is in _____.
A. Class One
B. Class Two
C. Class Three
5. These students are _____.
A. English
B. Chinese
C. boys
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多项选择题

处在急性期的病人，由于病情急，变化大，其情绪容易出现（）

A.冷漠

B.焦虑

C.恐惧

D.厌恶

E.绝望
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