The police failed to e up with evidence, and on that account the suspect was released.
A. effective
B. valid
C. subtle
D. considerate
网友回答
A. effective
(答案→)B. valid
C. subtle
D. considerate
解析：词义辨析. A.有效地;实际的;起作用的 B. 有根据的;正当的 C.微妙的;狡猾的 D. 体贴的;考虑周到的.根据题意,警方不能提供有效地证据,由于这个原因嫌疑犯被释放了.故选B,证据应该是有根据的.