Answer:
A average is a number expressing the central or typical value in a set of data. add up all the numbers, then divide by how many numbers there are.
Explanation:
I believe the answer would be D.
Sodium loses an electron and chlorine gains an electron.
First we will calculate the number of moles of Iron:

, where n is the number of moles, m is the mass of iron in the reaction and M is the Atomic weight.

moles of Iron.
The same number of moles of Oxygen will take part in the reaction.
So

where 32 is the Atomical Weight of Oxygen (16 x 2).
=>

g