A:蚯蚓要爬出地面呼吸
B:蚯蚓爬出地面取食
C:蚯蚓要爬出地面散热
D:蚯蚓喜欢在潮湿的地面爬行
如图1,在直角梯形ABCD中,∠ADC=90°,CD∥AB,AB=4,AD=CD=2.将△ADC沿AC折起,使平面ADC⊥平面ABC,得到几何体D﹣ABC,如图2所示.
(Ⅰ)求证:BC⊥平面ACD;
(Ⅱ)求几何体D﹣ABC的体积.
Sarah's home is a little far from her school. So she always _______ to school.