A:BD∥平面CB1D1
B:AC1⊥BD
C:异面直线AD与CB1角为60°
D:AC1⊥平面CB1D1
若干量x,y满足约束条件x+y≥1y-x≤1x≤1,则z=2x-y的最小值为()
Mr. Green lives on the ____(three)floor.