Packet-switching wireless networks are preferable(71)when transmissions are(72)because of the way charges are(73)per packet. Circuit-switched networks are preferable for transferring large files or for other lengthy transmissions because customers are(74)for the(75)of time they use the network.A．toB．forC．thanD．only
Packet-switching wireless networks are preferable(71)when transmissions are(72)because of the way charges are(73)per packet. Circuit-switched networks are preferable for transferring large files or for other lengthy transmissions because customers are(74)for the(75)of time they use the network.
A．to
B．for
C．than
D．only
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