根据试验结果，4万吨油轮在停车后余速约（）时无舵效
A.2.2节
B.3.2节
C.4.2节
D.5.2节
参考答案：B
Nowadays people are more concerned about the environment ________ they live.
A．what
B．which
C．when
D．where
用于去除污水中悬浮物的工艺有______。
A．沉淀
B．砂滤
C．气浮
D．离子交换
