单项选择题

Activity中如果加载多个Fragment,切换显示第三个Fragment,下面的代码哪些能实现?()

A.replaceFragment(R.id.main_fm,new Fragment1())
B.replaceFragment(R.id.main_fm,new Fragment2())
C.replaceFragment(R.id.main_fm,new Fragment3())
D.replaceFragment(R.id.main_fm,new Fragment4())