Which describes the molecular behavior of a solid? i think it's a, but im not sure

a. molecules vibrate around a fixed point.
b. molecules are too far apart to affect each other.
c. molecules have the greatest energy of motion.
d. molecules are rigid and do not move.

When 13.3 g koh is dissolved in 102.7 g of water in a coffee-cup calorimeter, the temperature rises from 21.4 °c to 31.53 °c. what is the enthalpy change per gram of koh (j/g) dissolved in the water? * take the density of water as 1.00 g/ml. * assume that the solution has a specific heat capacity of 4.18 j/g*k. enter to 1 decimal place. do not forget the appropriate sign /(+). canvas may auto-delete the (+) sign