The correct answer is B) Blower timing gears. In a Roots-type blower, the timing gears are responsible for ensuring that the two lobes of the blower do not make contact with each other during operation. The timing gears synchronize the rotation of the two lobes, keeping them from colliding and causing damage to the blower. This is a critical design feature that prevents the lobes from making contact. The other options are incorrect because they do not directly address the issue of preventing lobe contact. A drive chain, air trapped between the lobes, or an oil filter would not be the primary design elements responsible for maintaining the proper timing and clearance between the blower lobes.