Explanation

Desert grasslands are hot during the day, so animals are typically nocturnal or crepuscular to avoid heat. Diurnal (day-active) is incorrect as stated in the options if it implies daytime activity in peak heat, but fossorial (burrowing) is a common adaptation for escaping extreme temperatures and predators in deserts. However, 'relatively more abundant' usually refers to diurnal vs nocturnal patterns where many desert animals are nocturnal. Wait, let's re-evaluate. In hot deserts, animals avoid daytime heat by being nocturnal or burrowing (fossorial). Fossorial animals live underground, escaping the surface heat. This is a very strong adaptation in deserts. Diurnal animals exist but are less abundant than nocturnal/fossorial ones to avoid heat stress. Therefore, D is likely correct.