Please read every sentence _______. The more _______ you are, the fewer mistakes you'll make.
A:carefully; carefully
B:careful; careful
C:carefully; careful
D:careful; carefully
高铁酸钾(K2FeO4)是新型、高效的水处理剂,其氧化性比氯气、臭氧等更强,遇水易变化,在水处理过程中高铁酸钾被还原为Fe3+.则
(1)高铁酸钾中铁元素的化合价为 ____ .
(2)高铁酸钾除能消毒、杀菌外,还能除去水中的悬浮颗粒的原因是 ____ (用离子方程式表示).