题目

Baidu, the online search giant, launched its own Siri-like virtual assistant on Tuesday ________ is able, for instance, to place takeout orders. A. whatB. whoseC. whichD. whom 答案：A 氯化钠溶液中混有少量碳酸钠，为了除去碳酸钠，可加入适量 A． 氢氧化钠溶液 B． 稀硫酸 C． 盐酸 D． 氢氧化钙溶液