A:1+1i
B:1+i
C:1-1i
D:1-i
下列有关秦岭—淮河一线地理意义的叙述,正确的是( )
The little girl was ____ ____ ____ to face her mistake.
如图,已知梯形ABCD中,AD∥BC,∠C=90°,以CD为直径的圆与AB相切,AB=6,求梯形ABCD的中位线长.