I thanked him, and, turning from the main road, we entered a grass-grown by-path, which, in half an hour, nearly lost itself in a dense forest, clothing the base of a mountain.
In this sentence from the second paragraph of the passage, the phrase clothing the base of the mountain is used
A) to suggest that the mountain forest is impenetrable.
B) to suggest that the trees looked like clothes on the mountain.
C) to provide directions for the path through the mountain forest.
D) to describe the way that the trees surrounded the base of the mountain.