The police ________ a careful search of the block, but failed to find the suspect.A.put out B.turned out C.came out D.carried out 答案:【答案】D【解析】句意:警察对街区进行了仔细的搜查,但没有找到嫌疑犯。考查动词短语。put out熄灭;turned out结果;came out出版;carried out执行,实施。根据下文“but failed to find the suspect.”可知,这里是进行了仔细地搜索。这里用carried out。故选D。已知数列的前n项和为,且, 则等于
( )
(A) 4 (B)2
(C)1 (D) -2