Answer Happy

Can I get a sound proof for this.
Consider the two functions ƒ : A → B and g : B → C' for non-empty sets A, B, C. Decide whether each of the following statements is true or false, and prove each claim. a) If g of is injective, then g is injective. b) If g of is injective, then f is injective. c) If g of is surjective and g is injective, then f is surjective.