The correct option is C Most of
Option B: 'Most of' tells us an unspecified amount or number of a specific group of people 'my friends' (where 'most' is a quantifier).
Hence this is the correct option.
Option A: 'Most' is a quantifier that modifies nouns. But, when the noun is preceded by an adjective like 'my', then a preposition must follow 'most'.
Hence this isn't the correct option.
Option D: Similarly, 'five' is a number, but since it isn't followed by any preposition, the meaning is left incomplete. Hence D is incorrect.
Option C: 'Of' means 'belonging to'. It's a preposition, and does not express the number of 'my people'. Hence this option isn't correct.