What are the common causes of emission failures in vehicles?

The most common causes of emission failures in vehicles often relate to components and systems that directly affect a vehicle’s exhaust emissions. Faulty oxygen sensors, for instance, play a critical role in measuring the amount of oxygen in the exhaust gases and helping to adjust the air-fuel mixture for optimal combustion. If these sensors fail, they can result in an improper air-fuel mixture, leading to higher emissions.

Similarly, bad catalytic converters are essential for reducing harmful pollutants by converting them into less harmful substances before they exit the exhaust system. If a catalytic converter is malfunctioning or damaged, it can significantly increase a vehicle's emissions, leading to a failure during an emissions test.

Fuel system issues, such as a malfunctioning fuel injector or problems with the fuel pump, can also contribute to poor combustion and higher emissions, as they can lead to an improper fuel mixture being burned in the engine. Together, these components are crucial for ensuring that a vehicle meets emissions standards and minimizes its environmental impact.

The other options, such as outdated tires and brake issues, deal more with vehicle safety and performance rather than emissions control. Weak batteries and alternator failures primarily affect electrical systems, while interior air quality problems are not related to tailpipe emissions. Therefore, option B encompasses