果蝇是常用的遗传学研究的试验材料，据资料显示，果蝇约有104对基因，现有一黑腹果蝇的

写出下列命题的否定，并判断其真假

（1）3＝2

（2）5>4

（3）对任意实数x，x>0

（4）每个正方形是平行四边形

根据句意及首字母提示或单词的适当形式完成句子。

1. —I often make m _______ in the English compositions.

    —You should keep writing English diaries everyday.

2. She had difficulty f _______ this work.  It was too much for her.

3. —Can you p_______this word?

    —Sorry ,  I  can't.

4. Don't forget _______ ( have) a math exam tomorrow.

5. Don't run so quickly. Please walk here s_______.

6. He has some problems ________(work) out the math problem.

7.  The boy enjoys _______( memorize) the words of pop songs.

8.  _______( give)  it up would be like saying goodbye to an old friend.

马尾衬弹性大，挺括度高，常做高档服装的（）。

A、胸档

B、胸衬

C、拔头衬

D、肩垫衬

整流装置产生的内部过电压由并联于元件两端的（）进行保护。

合成氨反应：3H₂＋N₂2NH₃，其反应速率分别为v(H₂)，v(N₂)，v(NH₃)(用mol·L^－1·s^－1表示)，则正确的关系式是[ ]

A．v(H₂)＝v(N₂)＝v(NH₃)

B．v(N₂)＝2v(NH₃)

C．v(H₂)＝3/2v(NH₃)

D．v(N₂)＝3v(H₂)