人患禽流感的潜伏期是()
A.1~3天
B.7~10天
C.10~15天
D.15~30天
E.1~2个月
参考答案:A
The _____ of news that a flood is coming is a staff working in the weather bureau.
A.root
B.origin
C.source
D.resource
铰刀的切削厚度较小,磨损主要发生在后刀面上,所以重磨沿后刀面进行。