Was the door of the room _______ the whole day?    [ ]

A. remained opening                          

B. allowed open   

C. kept opened                                

D. left open

硫酸亚铁在强热下可发生反应:2FeSO₄Fe₂O₃+X+SO₃↑ ，则X的化学式是[ ]

A.S

B.FeO

C.SO₂

D.O₂