题目

 It was in the lab ______ was taken charge of by Professor Harris _______ they did the experiment. A. which, that            B. that, where C. whom, that            D. which, where 答案：Ａ下列化学式中只能表示一种物质的是（     ） Ａ.C3H7Cl          Ｂ.CH2Cl2            Ｃ.C2H6O           Ｄ.C2H4O2