Question

chord is at distance of zero cm from the centre of the circle of radius 17 cm find the length of the chord

Answer 1

chord is at the distance of 0 CM from chord
this is possible only when the centre point lies on chord.
therefore the chord is the diameter
we know that diameter is 2 times the radius
therefore diameter=2*17
=34cm

Answer 2

if the distance between the chord and the centre is 0 then the chord intersects the center and therefore is called a diameter.
to find diameter , we double the radius
d = 2*r
   = 2*17
   = 34 cm