Answer:
C.subscript
Step-by-step explanation:
The number 3 is a subscript on the hydrogen atom in ammonia NH₃.
Subscript is a lower notation on a reference atom. It states the number of hydrogen atom covalently bonding with the single N atom.
The superscript is located up. For example P², the 2 is a superscript.
The coefficient is the number before a compound or atom e.g 2C represents two atoms of Carbon.
The numerator is the upper value in a fraction. The denominator is the one beneath.