Four gases are described below: Gas A: 3 liters at 42 °C Gas B: 9 liters at 12 °C Gas C: 9 liters at 42 °C Gas D: 9 liters at 12 °C Which gases have the same average molecular kinetic energy?

Average kinetic molecular energy is actually defined by temperature, so any gas, no matter the volume or pressure, will have the same average kinetic molecular energy as long as its temperature is the same. Therefore, Gases A, B, and D all have the same average molecular kinetic energy, since they are at 12 °C.