Final answer:
In constructing a lean-to shelter, the bough butt ends should be oriented towards the ground for water runoff and stability. The mention of lichens on trees is related to traditional navigation skills taught to boy scouts, with lichens growing on the shaded north side of trees.
Step-by-step explanation:
When building a lean-to shelter, the bough butt ends should be pointing towards the ground, which is option b). This orientation ensures that water runs off the boughs without getting into the shelter and provides overall structural stability. It's useful to remember that the sun's path curves across the southern sky, resulting in the north side of tree trunks typically being more shaded. This fact was traditionally taught to boy scouts for directional guidance, indicating that lichens would predominantly grow on the north side, away from direct sunlight.