My grandma often __________ stories to us.
A:speaks
B:talks
C:says
D:tells
(I)求证:直线DE⊥平面PAC.
(Ⅱ)若直线PE与平面PAC所成的角的正弦值为 55 ,求二面角A﹣PC﹣D的平面角的余弦值.
-Who invented the light bulb?
-It was invented ____________ Edison.