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问题 单项选择题

甲数除以13余7，乙数除以13余9，现将甲乙两数相乘，积除以13的余数应是（）。

A．3

B．7

C．11

D．12

答案

参考答案：C

解析：设甲为13a+7，乙为13b+9，a、b均为整数，则根据题意得（13a+7）（13b+9）=169ab+13（9a+7b）+63，故甲乙两数之积除以13的余数即为63除以13的余数，余数为11。故本题选C。

问答题

阅读资料1～4，请概括资料反映了哪些问题现象。
要求：紧扣给定资料，语言简洁，概括全面，有条理，不超过200字。
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单项选择题

The great advance (91) rocket theory 40 years ago showed that liquid-fuel rockets were far (92) in every respect to the skyrocket with its weak solid fuel, the only kind of rocket then known. (93) , during the last decade, large solid-fuel rockets with (94) fuels about as powerful as liquid fuels have (95) their appearance, and it is a favorite layperson’s question to (96) which one is "better". The question is meaningless. (97) might as well ask whether a gasoline or a diesel engine is "better". It all (98) on the purpose. A liquid-fuel rocket is complicated, (99) has the advantage that it can be controlled beautifully. The burning of the rocket engine can be stopped completely; it can be reignited when (100) . (101) , the thrust can be made to vary by adjusting the speed of the fuel pumps. A solid-fuel rocket, on the other hand, is rather (102) in construction, (103) hard to build when a really (104) size is desired. But once you have a solid-fuel rocket, it is ready for action (105) very short notice. A liquid-fuel rocket has to be fueled first and cannot be (106) readiness for very long after it has been fueled. (107) , once a solid-fuel rocket has been ignited, it will keep burning. It cannot be stopped and reignited (108) desired (it could conceivably be stopped and reignited after a pre-calculated time of burning has elapsed, and its thrust cannot be varied. Because a solid-fuel rocket can be kept ready for a long time, most military missiles (109) solid fuels, but human-piloted spaceflight needs the fine adjustments that can (110) be provided by liquid fuels.

A．should

B．when

C．though

D．if
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