The correct option is B 2x+y−3=0
Given, equation of the circle is (x−2)2+(y+1)2=16 and equation of chord is x−2y−3=0
Perpendicular drawn to the chord from the centre bisects it.
Hence, the diameter which bisects the chord is perpendicular to it.
Equation of the line passing through (2,−1) with slope m=−2 is 2x+y−3=0
∴ Required equation of diameter is 2x+y−3=0
Hence, option B.