题干
Jim tried hard，and finally he ______ his dream of being the best football player in his school.
A：recognised
B：realised
C：organised
D：reviewed
答案(点此获取答案解析）
B
离子在一定条件下可把Mn2＋氧化成
，若反应后
变成
，又知反应中氧化剂与还原剂的离子个数比为5:2，则