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问题 选择题

It has been raining for a day, but even though it hadn’t rained, we ________ there by tomorrow.

A．can’t get

B．won’t get

C．hadn’t got

D．wouldn’t get

答案

答案：A

we can’t get there by tomorrow 为客观事实，故宜用陈述语气。

单项选择题

当正线行车间隔在（）分钟及以内发生SICAS故障时，采用“目视行车法”组织行车。

A.2

B.3

C.4

D.5
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单项选择题

The usual way to ensure reliable delivery is to provide the (16) with some feedback about what is happening at the other end of the line. Typically, the protocol calls for the receiver to send back special (17) frame bearing positive or negative (18) about the incoming frames. If the sender receives a positive acknowledgement about a frame, it knows the frame has arrived safely.On the other hand, a negative acknowledgement means that something has gone wrong, and the frame must be transmitted again. An additional complication comes from the possibility that hardware troubles may cause a frame to (19) completely. In this case, the receiver will not react at all, since it has no any reason to react. It should be clear that a protocol in which the sender transmits a frame and then waits for an acknowledgement, positive or negative, will hang forever if a frame is ever lost due to, for example, (20) hardware.

（18）是（）

A. application

B. connection

C. stream

D. acknowledgement
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