which prefix is used to indicate that the main chain of a hydrocarbon contains four carbon…

Brief Explanations:

In organic chemistry, the prefix "but-" is used to denote a hydrocarbon chain with four carbon - atoms. For example, butane has four carbon atoms in its main chain. "Quad -" is not a common prefix in hydrocarbon nomenclature. "Non -" indicates nine carbon atoms. "Prop -" indicates three carbon atoms.

Answer:

C. but-