When balancing a chemical equation it is OK to change...?10 POINTS!

When balancing a chemical equation it is OK to change:
Answer
A.
the subscripts in the formulas
B.
the number of atoms of each element in the formulas
C.
the coefficients in front of the formulas
D.
the formulas

The coefficients, which are the numbers in front of each molecule in a stoichiometry equation, are the ONLY things you CAN change.
Everything else is untouchable, since it would mean changing the formulae of the molecules involved.

C.
the coefficients in front of the formulas