According to Illinois CDL regulations, which vehicles are subject to a semi-annual safety inspection?

Answer: D — Trucks with a gross weight of more than 8,000 pounds

In Illinois, vehicles with a gross weight of more than 8,000 pounds are subject to a semi-annual safety inspection. This includes trucks falling under this weight category, as outlined in the CDL regulations. It's important to comply with these inspections to ensure the safe operation of larger vehicles on the road. Options A and B are below the specified weight threshold, so they would not be subject to the semi-annual safety inspection. Option C specifically mentions motor buses and religious buses, which are subject to separate regulations and inspections, not covered by the semi-annual safety inspections mentioned in the question.