— ______.
A:Sounds good
B:Fine, thank you
C:That's right
D:It's windy
计算:﹣1317×19﹣1317×15=____
(I)求证:DE∥平面A1C1B;
(II)求直线DE与平面ABB1A1所成的角的正弦值.
——Would you mind if I sit here?—— It's for Miss Zhou.