Which of these chemical elements are commonly found in petroleum products?

Petroleum products primarily consist of hydrocarbons, which are compounds made up of hydrogen and carbon. Therefore, the presence of hydrogen and carbon in petroleum products is essential, as they directly contribute to the fuel's energy content and physical properties.

Sulfur, while not a primary component, is also commonly found in petroleum products, albeit in smaller quantities. It can affect the quality of fuels and is regulated in many applications to reduce pollution and enhance combustion efficiency.

The other elements listed in the other options are either not prevalent in significant amounts in petroleum products or are primarily associated with different types of materials. For example, while nitrogen and oxygen are present in trace amounts in some petroleum products, they do not play a significant role compared to hydrogen and carbon. Phosphorus and potassium are largely unrelated to petroleum chemistry, typically associated with biological and agricultural contexts. Similarly, silicon and calcium are elements more relevant in other industrial materials than in petroleum derivatives.