Tonya and Mario are asked to use a pan balance to find the mass of the same rock. Tonya finds the rock's mass to be 680 grams. Mario finds the rock's mass to be 672 grams. Which is the best explanation for the difference in their measurements? A. Either Mario or Tonya measured the mass of the rock incorrectly on the pan balance.

B. The rock was cold when Tonya measured its mass and hot when Mario measured in mass.

C. The rock changed in size between the time Tonya measured it and the time Mario measured it.

D. The rock broke before Mario measured it. So the mass of the two pieces together was less than when Tonya measured it.