When the timing gear backlash for a Roots-type blower has become excessive, the problem is properly repaired by __________.

Correct Answer: Option C — renewing both driving and driven gears as a set

Roots-type blower timing gears operate with tight tolerances and match wear patterns over time. Replacing only one gear creates uneven meshing, excessive backlash, and rapid tooth destruction. Renewing both as a matched set ensures proper tooth clearance and load distribution.