A:this; have
B:that; to have
C:it's; to have
D:it's; have
以抛物线C的顶点为圆心的圆交C于A、B两点,交C的标准线于D、E两点.已知|AB|= 42 ,|DE|= 25 ,则C的焦点到准线的距离为( )
Mr Jackson hasn't decided this weekend.