Question

particulates from modern engines are usually small particles of

a. oxygen
b. hydrogen
c. carbon
d. iron

Explanation:

Modern engines, especially internal - combustion engines, burn fuel (which is mainly composed of hydrocarbons). When the combustion is incomplete, small particles of carbon (soot) are formed. Oxygen (\(O_2\)) is a reactant in combustion (not a particulate product in this context). Hydrogen (\(H_2\)) is also part of the fuel but is not the particulate product. Iron (\(Fe\)) is not a common component of engine fuel in a form that would produce iron particulates in normal engine operation.

Answer:

C. Carbon