题目

Knowing how long the test would last, the students who finished ______ back and waited until the end of the exam.   A. settle    B. settled     C. settling    D. to settle 答案：B硝酸与一定量的铁充分反应，则溶液中(  )A．一定会有Fe2＋B．可能含Fe2＋C．一定含Fe3＋D．可能含Fe3＋