A
Air molecules touch the warm ground, heating them up is the best statement best describes heating by conduction
Step-by-step explanation:
Conduction occurs when a molecule that is close together pass along energy due to the bombardment between them as they gain kinetic energy. In this case, particles of the warm ground have higher kinetic energy than those of the air. When the molecules of the two collide the higher kinetic energy of the ground molecules is transferred to the air molecules . This is how the air also gets warmer.
Choices B & D show heat transfer by convection while choice C shows heat transfer by radiation.