Answer:
Curved tree trunks are usually an indication of (A) solifluction.
Step-by-step explanation:
The curvature of tree trunks is often a result of solifluction, a type of mass movement where soil moves slowly downslope, typically in areas with saturated ground. This process is common in periglacial regions, where freezing and thawing of the soil create a slushy layer that can cause the gradual downslope movement of material. As the soil moves, it can deform the tree trunks, leading to a characteristic curvature.
Solifluction is a geologic process influenced by factors such as climate, soil composition, and topography. It is essential to recognize these signs in landscapes to understand the geological history and ongoing processes in a particular area. Identifying the indicators, like curved tree trunks, helps geologists and environmental scientists decipher the dynamic interactions shaping the Earth's surface.
Option A is correct.