题目

--Would you please explain to me about the difference between the two phenomenon?    --I’m sorry, but that’s just _____ I’m puzzled about. A. why          B. what             C. which          D. where 答案：B在下列反应中，水只作氧化剂的是          （　　）   A．2Na + 2H2O ＝ 2NaOH + H2↑          B．2F2 + 2H2O ＝ 4HF + O2 C．Cl2 + H2O ＝ HCl + HClO                 D．SO3 + H2O ＝ H2SO4