He ____ going to the beach.
Name
Favourite
Bob
Lucy
Mary
Jack
colour
blue
pink
green
clothes
shorts
dresses
sweaters
shirts
已知直线x+ay﹣1=0是圆C:x2+y2﹣4x﹣2y+1=0的对称轴,过点A(﹣4,a)作圆C的一条切线,切点为B,则|AB|=( )