Answer:
4. 15
Explanation:
The given formula is:- 
1 mole of the salt contains 2 moles of nitrogen atom, 8 moles of hydrogen, 1 mole of sulfur and 4 moles of oxygen atom as can be seen from the formula.
Thus,
1 mole of salt contains total of 15 moles of the atoms which constitute the salt.
<u>Hence, 4. is the answer.</u>
I would say D, because you need to start with nothing to measure the different sizes as they start to grow. hope this helps!
The answer is C I got it right so hope it helped ;)