Please need help Which of the following describes the molecules in a sample of water as the temperature of the water changes from 20°C to 30°C? A. The molecules speed up and their average kinetic energy increases. B. The molecules slow down and their average kinetic energy decreases. C. The molecules speed up and their average kinetic energy stays the same. D. The molecules slo w down and their average kinetic energy stays the same. following is the best example of heat transfer by radiation?