已知H-H键能为436KJ/mol，H-N键能为391KJ/mol，根据化学方程_爱下问搜题

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问题不定项选择题

已知H-H键能为436KJ/mol，H-N键能为391KJ/mol，根据化学方程式：N₂＋3H₂＝2NH₃ ΔH＝-92.4KJ/mol，则N≡N键的键能是[ ]

A．431 KJ/mol

B．946 KJ/mol

C．649 KJ/mol

D．869 KJ/mol

答案

答案：B

阅读理解

阅读下面一篇材料，从所给的A-G七个选项中，选出正确的选项填空，使短文通顺、内容完整。

    People all over the world do shopping in supermarkets. Who decides what you buy in the supermarkets?
1._____________
    When you go into the supermarket, you see shelves full of things.2.______________You pull a shopping
cart and put the things you choose in it.
   If you hear soft and slow music, you may walk slowly. If you hear fast and loud music, you may walk
quickly. 3._____________You walk slowly and have more time to choose things.
    Suppose you go to the meat department first. 4._____________The cheaper meat is at the other end of
the meat department, away from where the customers enter. You have to walk by all the expensive meant
before you find the cheaper one. 5.______________.
    That's some knowledge of supermarket science. Many supermarkets use such knowledge to make
customers stay longer and buy more.

A. Maybe you will buy some of the expensive meat instead of the cheaper meat.
B. You walk between the shelves.
C. That's why the supermarket plays slow and soft music.
D. The manager of the supermarket knows where the customers enter the meat department.
E. Do you decide or the supermarkets decide?
F. You may feel a little tired to find the cheapest meat.
G. You should learn some knowledge of supermarket science.

选择题

（理）在空间直角坐标系中有长方体ABCD-A₁B₁C₁D₁，AB=1，BC=2，AA₁=3，则点B到直线A₁C的距离为（　　）