A,B,C are three planets with the same mass,then it means they have also the same gravity,so what matters here is the distance between the Sun,more exactly,their orbits.
⇒ The shorter the distance from the Sun, the more a planet completes an orbit. ⇒ Correct affirmation : Planet A will take the shortest time to complete an orbit, while planet C will take the longest time.
The first affirmation is false because the planet A is the closest to Sun,so logically,it will complete the orbit faster than the others.
The affirmations 3 and 4 are incorrect because their gravity is equal and because the distance between the planets and the Sun differs from one planet to another.
