We _____ into five groups to go to the old people's homes. We did many things to cheer them up. [     ]

A. divided

B. are divided

C. were divided

关于阿尔茨海默病发病机制描述错误的是（）

A.遗传因素

B.脑外伤、铝中毒、吸烟等环境因素

C.乙酰胆碱和谷氨酸等神经递质的减少

D.神经递质受体的减少

E.与免疫功能缺陷无关