水稻褐飞虱的防治适期是()盛发期施药。
A、成虫
B、产卵
C、二至三令若虫
D、一令若虫
参考答案:C
So seriously _____ in the accident that he was sent to hospital at once.
A.he was wounded
B.was he hurt
C.he did injure
D.did he hurt
不垂直、相交孔系一般指孔系之间轴心线夹角不是90°的。