El jamón está bueno, señor.
a. cómprelo b. cómprela c. cómprelos

This is a command. Commands are sentences defined as imperative mood. Put another way, the imperative mood is used to tell someone to do something in a direct manner. Cómprelo is the correct conjugation of the verb comprar in formal form and for singular nouns. Put simply, here someone is selling ham (jamón) that is a singular noun. On the othe hand, Señor (Sir)  makes the sentence to be formal.

ancient india is often called the harappan civilization because one of the ancient cities was called harappa. harappa was just one of 1500 cities in the indus river valley. another well-known city is called mohenjo-daro. historians estimate ancient india to be the biggest of all four early civilizations.