Answer: C. leaf loss
One biome which exhibits four distinct seasons is the deciduous forests. Leaves are known to be the main producing organs of food in plants. Leaves are where many metabolic functions like respiration take place. Deciduous trees are known to possess broad leaves and during fall, these leaves tend to fall off.
This falling of leaves during autumn is important as it helps the tree in regulating soil moisture and temperature levels as well as in the addition of nutrients in the soil. During the winter months, the trees shed their leaves so as not to lose moisture from the surrounding ground now littered by leaves. These fallen leaves will in turn decompose and then add nutrients to the soil. With this more food is produced by the plant even during the toughest seasons.