有风点源扩散模式中，排气筒有效高度Ho是指（）。
A.混合层高度
B.烟气抬升高度
C.排气筒髙度与烟气抬升髙度之和
D.排气筒高度
参考答案：C
阅读理解，判断正(T)误(F)。
Summer is coming. The summer sun is very hot. Li Ming likes summer. In summer he puts on his shorts,
T-shirt and sandals.
He likes to go for a walk with his parents. Sometimes he goes swimming and plays ping-pong with his
friends. He thinks summer is so fun.
( ) 1. Summer is very hot.
( ) 2. Li Ming doesn't like summer.
( ) 3. Li Ming likes to go for a walk.
( ) 4. Li Ming never goes swimming.
( ) 5. He thinks summer is so fun.
合同责任的完成必须通过( )来保证。
A．经济手段
B．技术手段
C．管理手段
D．行政手段
