下列命题中正确的是( )
A．若
收敛，则
必收敛
B．若
与
都发散，则
必发散
C．若
，则
必发散
D．若
收敛，则必有
参考答案：C
解析： 本题考查数项级数的审敛．
[要点透析] 可用排除法，A选项对于交错级数不成立；对于B选项，若
，则
与
都发散，但
收敛，故B选项错误；对于D选项，当
收敛时，
有可能为1，故D选项错误；则选C．
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| After the earthquake took place (发生), I found 1 in the dark. I couldn't move. The bottom (底部) parts of 2 my legs and my feet were hurting 3 . All around me was quiet. But below me I could hear shouts and a lot of noise. Then I remembered 4 had happened, I had been in an earthquake. For about two hours nobody came. 5 I could reach the bag of apples, so at least I had much to eat. Then I heard people 6 to me. A team of people had come to see 7 anyone was under the broken road. I called out "I'm here!" I heard a shout. Soon a stranger climbed to the bridge near my car. "How are you doing?" he asked. "Not too bad," I said. "but my feet and legs feel 8 they're broken", "we'll do our best 9 you out of there," he said. They didn't get me out 10 the next morning. I had been in my car for fourteen hours. | ||||
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