A:in where
B:in which
C:where
D:the place where
—Yes. I cough and feel very upset today.
(Ⅰ)求证:面ADE⊥面 BDE;
(Ⅱ)求直线AD与平面DCE所成角的正弦值..
下列各句中,没有语病的一项是 ( )