Even though bilge keels do provide some improvement in longitudinal strength at the bilge radius, what is the primary purpose of the bilge keels?

Correct Answer: Option C — Dampen the tendency the ship has to roll.

Bilge keels are external appendages fitted to the turn of the bilge. Their primary hydrodynamic function is to increase the vessel's resistance to rolling by creating drag as the ship moves through the water, thereby effectively dampening the amplitude of roll motions.