立管的重量少过多少公斤可以不需要安装底部支承？
A.100公斤
B.70公斤
C.50公斤
参考答案：A
Read and write.(按要求完成句子)
1. I read a book yesterday. (就画线部分提问)
________________________________________________
2. She went to the park last weekend. (就画线部分提问)
The children were catching butterflies in the garden. Some caught a lot, and others caught _______at all.
A．nothing
B．none
C．no one
D．neither
