题目

The parents left their eldest son Daniel __________ of their house while they were away. A. in the charge  B. in charge  C. in his charge  D. in a charge 答案：B 设nA为阿伏加德罗常数的数值。下列说法正确的是  (　　) A．常温下，4 g CH4含有nA个C—H共价键 B．1 mol Fe与足量的稀HNO3反应，转移2 nA个电子 C．1 L 0.1 mol·L－1NaHCO3溶液中含有0.1nA个HCO D．常温常压下，22.4 L的NO2和CO2混合气体含有2 nA个O原子