_______ the composition, John handed it to the teacher and went out of the room.　

A．Writing　　　

B．Having written 　

C．Written　　　

D．Being written

某中学为了解学生近视的患病情况，在6个年级56个班3000人中抽取600人进行视力检查，最合适的随机抽样方法是（）

A.单纯随机抽样

B.系统抽样

C.分层抽样

D.整群抽样

E.分层整群抽样