C. The drawing is correct, because there are eight white atoms and eight red atoms on each side of the reaction.
The law of conservation of matter is quite simple. Matter may be neither created, nor destroyed. So looking at the drawing, on the left side, there's 4 molecules, each of which has 2 large red atoms and 2 small white atoms for a total of 8 large red and 8 small white atoms. And if you look at the right side, there's a different combination of different molecules, but they still add up to 8 large red and 8 small white. And of the available options, only "C" matches.
