A:6个亲本都是杂合体
B:抗病对感病为显性
C:红种皮对白种皮为显性
D:这两对性状自由组合
I could hardly hear her at the back.
(Ⅰ)求证:BE⊥平面AD′C;
(Ⅱ)求平面D′AB与平面D′CE的所夹的锐二面角的大小.
2+9=____,11-9=____,11-2=____