The correct answer is: A. Lowering sulfur content in fuel.
The Euro II standard is an emission standard for vehicles that was introduced in 1996. It limits the amount of sulfur that can be present in fuel, which helps to reduce air pollution. Sulfur in fuel can react with oxygen in the air to form sulfur dioxide, which is a major contributor to acid rain.
The Euro II standard also limits the amount of nitrogen oxides (NOx) and particulate matter (PM) that can be emitted by vehicles. NOx and PM are both pollutants that can cause respiratory problems and other health issues.
The Euro II standard was followed by the Euro III, Euro IV, Euro V, and Euro VI standards, which have progressively stricter emission limits. The Euro VI standard is the most recent standard and was introduced in 2014.
The Euro standards are an important part of the effort to reduce air pollution from vehicles. By limiting the amount of pollutants that can be emitted, the Euro standards help to improve air quality and protect public health.
Here is a brief explanation of each option:
- Option A: Lowering sulfur content in fuel. This is the correct answer. The Euro II standard limits the amount of sulfur that can be present in fuel, which helps to reduce air pollution.
- Option B: Increasing sulfur content in fuel. This is not the correct answer. The Euro II standard limits the amount of sulfur that can be present in fuel, not increases it.
- Option C: Lowering carbon content in fuel. This is not the correct answer. The Euro II standard does not limit the amount of carbon that can be present in fuel.
- Option D: Increasing carbon content in fuel. This is not the correct answer. The Euro II standard does not limit the amount of carbon that can be present in fuel.