与小肠吸收营养物质无关的结构特点是( )
____A. Drink some water.
____B. Have some milk.
____C. I'm six years old.
____D. Act like a tiger.
____E. I'd like some eggs.
已经平行四边形ABCD中,AB=4,E为AB的中点,且△ADE是等边三角形,沿DE把△ADE折起至A1DE的位置,使得A1C=4.(1)F是线段A1C的中点,求证:BF∥平面A1DE;
(2)求证:A1D⊥CE;
(3)求点A1到平面BCDE的距离.