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问题 选择题

用所学化学知识判断下列研究成果或报道可能不属实的是     （   ）

A．某山区发现了一种“柴油树”，它产生的树油可替代柴油使用

B．新型材料碳纳米管的化学性质常温下很稳定

C．美国最新研制出一种燃料电池，其能量转化率很高，可达到100％

D．蜘蛛丝（主要成分是蛋白质分子）强度特别大，可以用来制造防弹衣和降落伞绳

答案

答案：C

任何电池在能量的转化过程中都有损耗，故答案为C

单项选择题

某宫颈癌患者腔内治疗时，1次／周，6Gy／次，照射时间为15分钟，该治疗属于（）。

A.中剂量率腔内照射

B.中高剂量率腔内照射

C.低剂量率腔内照射

D.高剂量率腔内照射

E.以上都不是
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单项选择题

The usual way to ensure reliable delivery is to provide the （71） 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 （72） frame bearing positive or negative （73） about the incoming frames. If the sender receives a positive acknowledgement about a frame, it knows the 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 （74） 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, （75） hardware.。

A．vanish

B．vary

C．appear

D．incline
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