Final answer:
The defect in the suspension system from the given options is a loose tie rod, which can cause poor vehicle handling and potentially unsafe driving conditions.
Step-by-step explanation:
The example of a defect in the suspension system is c. Loose tie rod. The suspension system is responsible for maintaining vehicle stability and handling by keeping the tires in contact with the road surface. A loose tie rod can impact the wheel alignment, causing the vehicle to pull to one side or the steering to feel loose, which can be dangerous and indicate suspension problems. Other options, such as worn-out tires, low engine oil level, and a dirty air filter, affect other systems such as the tires, engine, and the vehicle's air intake system, respectively.