Final answer:
Wet clothes drying on a warm summer day undergo evaporation, which is a phase change from liquid to gas requiring energy.
Step-by-step explanation:
When wet clothes dry on a warm summer day, the water in the clothes undergoes a process called evaporation. During evaporation, the phase change happens from liquid to gas. This phase change requires energy to overcome the molecular attraction between water molecules in the liquid state. Hence, energy is absorbed from the surroundings (in this case, from the air and the sun's warmth), allowing the water molecules to escape into the air as vapor. Therefore, the correct answer to the question is d) Evaporation - Requires energy.