Packet-switching wireless networks are preferable (1) when transmissions are (2) because 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.

3（）

A．computing

B．incurious

C．incurred

D．incurred

木质化细胞壁可用下列哪种试液鉴别

A．氯化锌碘

B．硫酸

C．间苯三酚

D．钌红

E．苏丹Ⅲ