何谓水汽头边界？
参考答案：
水汽图上边界整齐光滑，向上游一侧凸起，一侧为里冷的湿区和高云区，另一侧为狭窄的干黑带。
As a young man, Comrade Zhou Enlai _____ the students movements and later _____ the Communist
Party of China. [ ]
A. joined; took part in
B. took part in; joined
C. joined in; took part in
D. took part in; joined in
上请制度
