一There's something wrong with my car. I will after work.
A:fix up it
B:fix it up
C:set up it
D:set it up
如图,在Rt△ABC中,∠ACB=90°,AB的垂直平分线DE交AC于E,交BC的延长线于F,若∠F=30°,BE=4,则AD的长是( )