Question

when is di- used in the name of a hydrocarbon? when the main chain contains two carbon atoms when there are two different substituents when there are two main chains of equal length when there are two identical substituents

Explanation:

In hydrocarbon nomenclature, the prefix "di -" is used to indicate the presence of two identical substituents. For example, dimethyl means two methyl groups.

Answer:

when there are two identical substituents