____
A. Open the door.
B. Turn on the light.
C. Clean the blackboard.
D. Clean the window.
E. Put up the picture.
(2016•山东)已知数列{an}的前n项和Sn=3n2+8n,{bn}是等差数列,且an=bn+bn+1.
需____
确____
许____
刻____