Question

Please help. Thank you guys for all your help and support. <3

Answer 1

Option D, to obey the conservation of mass.

The conservation of mass essentially states that all the atoms in a chemical reaction will still be there once the chemical reaction is complete.
Because of this, you have to balance chemical equations in order to ensure that there isn't a surplus or deficit of atoms on either side.

-T.B.

Answer 2

It would be “To obey the law of conservation of mass”