A:①②③④
B:①②③
C:②③④
D:①②④
His grandfather ____ ____ a lot of hardships during the war.
设α﹑β为钝角,且sinα=55,cosβ=﹣31010,则α+β的值为( )
①自习课上,同学们安静地学习
②一个小女孩在个人独处的场合将果皮扔进垃圾箱
③一位男生躲在校园的角落里吸烟
④非得在老师的监督下才完成作业