题目

 The fellow was caught stealing and is nowin the police station. A. watching over                    B. watching out for C. being watched over               D. being watched out for 答案：【解析】选C。考查动词短语辨析及语态。watch out for “当心; 提防” ; watch over “看守” 。根据句式结构, 此句应为被动句即他正在警察局被看守着, 所以只有C项正确。将15mL 2mol·L-1 Na2CO3溶液逐滴加入到40mL 0.5mol/LMCln盐溶液中，恰好将溶液中的Mn+离子完全沉淀为碳酸盐，则MCln中的n值是A．4 B．3C．2D．1