Which of the following statements is correct?

Can you guys me with question no. 5!

Which formula can be used to calculate the molar mass of ammonia (nh3)? molar mass of n + molar mass of h 3 × molar mass of n + molar mass of h molar mass of n + 3 × molar mass of h 3 × molar mass of n + 3 × molar mass of h

Can someone me with 3 and 4 plz. this is for masteries test.