题目

 Peter was ______ to come to school this morning. A. a second         B. the second  C. a No. two        D. the two 答案：B4．掌握化学用语是学好化学的关键．下列化学用语与含义相符的是（　　）A．Fe3O4_______四氧化三铁B．2H______2个氢元素C．O2________2个氧原子D．Na______钠离子