Answer:
option: A is correct( i.e. line segment BF)
Explanation:
" A radius can be a line from any point on the circumference to the center of the circle and If you put two radii together, edge to edge, going through the center of a circle, you would get a diameter " .
from the following figure we could clearly see that F is the center of the circle.
and the line segment that touches the circle from the center is BF.
whereas line segment AC,BE are the diameters of the circle.
and AB is a chord.
Hence, option A is correct i.e. the radius of the circle is BF.