Which compensates for induced magnetism in the horizontal soft iron of a vessel?

Correct Answer: Option B — Iron spheres mounted on the binnacle

Quadrantal deviation is caused by induced magnetism in horizontal soft iron. To compensate for this, soft iron spheres are placed on the binnacle athwartships of the compass. These spheres are adjusted to neutralize the horizontal magnetic influence, thereby correcting the deviation caused by the vessel's horizontal soft iron.