出现什么情况时,应停止放煤?
参考答案:
煤壁片帮、冒顶时;井下放煤出现泥沙;瓦斯量突然增大;工作面涌水量突然增大。
如图为家鸽的呼吸系统和气囊结构示意图,能够发生气体交换的是( )
A.a和b
B.b和c
C.b
D.c
The number of deaths from heart disease will be reduced greatly if people ____ to ear more fruit and vitamins.
A.persuade
B.will persuade
C.be persuade
D.are persuaded