The following question, consist of two words each that have a certain relationship to each other, followed by four lettered pairs of words. Select the lettered pair that has the same relationship as the original pair of words: Mountain : Hill :: Tree : ?

The answer is B. Leaf.

In the original pair, "mountain" is a larger and more complex landform than "hill." Similarly, a "tree" is a larger and more complex plant than a "leaf."

The other options do not have the same relationship. "Ground" is not a larger or more complex version of "mountain." "Forest" is a collection of trees, not a larger or more complex version of a tree. "Shrub" is a type of plant that is smaller and less complex than a tree.