Answer:
I'm not single, i have me, myself and my looks. ;)
Explanation:
I'M CRINGING AS I WRITE THIS-
Perihelion is when a planet is closest to the sun and aphelion is when it is farthest from the sun. Perihelion is the correct answer.
The number of neutrons=Atomic mass-atomic number
no of neutrons=20-10
no of neutrons=10