Which parts of the car must be in good condition to prevent excessive noise and gas from entering the vehicle?

The exhaust system and engine are crucial components in minimizing excessive noise and preventing harmful gases from entering the vehicle cabin. A properly functioning exhaust system ensures that exhaust gases are efficiently directed away from the engine and out of the vehicle, reducing both noise and the risk of gas infiltrating the passenger area. Additionally, the engine's operation affects the exhaust system's efficiency; if the engine is misfiring or not operating correctly, it can lead to increased emissions and may cause the exhaust system to produce more noise than intended. Therefore, maintaining these parts ensures a quieter, safer driving experience, with less pollution entering the cabin.

The other choices focus on parts that, while important for overall vehicle safety and performance, do not specifically target noise and gas infiltration issues to the same extent. For instance, while the suspension and tires affect ride comfort and handling, they do not play a significant role in managing noise or gas emissions. Similarly, brakes and headlights are essential for safety but are not directly involved in controlling noise or exhaust, and the steering and transmission primarily impact vehicle control and power delivery rather than sound and gas management.