Question

Hydrocarbons _____. form when fuel is not completely burned are very poisonous are created mainly by factories are formed when fuel burns at high temperatures

Answer 1

It’s fuel because that’s what I got on my quiz and I got it right

Answer 2

Hydrocarbons form when fuel is not completely burned.

Step-by-step explanation:

Hydrocarbons form when fuel is not completely burned. Unlike many of the other gases, hydrocarbons are not poisonous. However they are a major pollutant because they combine with nitrogen oxides. This combined pollutant, together with particles of smoke and soot, forms smog. Automobile engines are the major source of hydrocarbons.