对于尘肺和职业肿瘤的调查尤其要注意()
A.车间人员和退休人员
B.退休人员和离职人员
C.在岗人员和对照人员
D.对照人员和车间人员
E.离职人员和车间人员
参考答案:B
Packet-switching wireless networks are preferable (1) when transmissions are (2) bemuse of the way charges are (3) per packet. Circuit-switched networks are preferable for transferring large files or for other lengthy transmissions because customers are (4) for the (5) of time they use the network.
1()
A.to
B.for
C.than
D.only
简述发展内因论。