题目

—Has John arrived at the hotel? —Not yet. He                     here              a couple of days. A. is;in B. will be;with C. was;before D. will be;in 答案：D人们在认识事物时可以采取多种分类方法。下列关于NaCl的分类不正确的是（   ）A．氧化物                   B．化合物            C．氯化物            D．钠盐