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问题 单项选择题

如再次使用同批号青霉素注射时，免做过敏试验要求间断时间不超过

A．1d

B．3d

C．5d

D．7d

E．14d

答案

参考答案：B

解析：青霉素治疗停药3d以上，须重新做过敏试验。因为停药3d，可能会有新的抗体产生，因此须重新进行过敏试验。

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.

（16）是（）

A.receiver

B.controller

C.sender

D.customer
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单项选择题

氨基酸在等电点时是

A．非极性分子
B．阴离子
C．阳离子
D．兼性离子
E．疏水分子
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