反应N2+3H2→2NH3的平均反应速率可表示为，也可表示为（）。
A.
B.
C.
D.
参考答案：B
Where are you going at this weekend, Sam?[ ]
A. I am going to do my homework.
B. I am cleaning the house.
C. I am going to the zoo with my brother.
D. I went to the park.
3分米=______厘米=______毫米．
