The correct answer is C. Bud : Flower.
A sapling is a young tree, while a flower is the reproductive structure of a plant. A bud is an undeveloped flower or leaf. A river is a large natural stream of water flowing in a channel to the sea, a lake, or another river. A brook is a small stream of water.
A sapling is to a tree as a bud is to a flower. A sapling is a young tree that has not yet reached maturity. A bud is an undeveloped flower or leaf. Both saplings and buds are in the early stages of development, and they both have the potential to grow into something larger and more complex.
A horse is not to a mare as a sapling is to a tree. A horse is an adult animal, while a mare is a female horse. A sapling is a young tree, and a tree is not necessarily an adult animal.
A student is not to a teacher as a sapling is to a tree. A student is a person who is learning, while a teacher is a person who teaches. A sapling is a young tree, and a tree is not necessarily a person who teaches.
A river is not to a brook as a sapling is to a tree. A river is a large natural stream of water, while a brook is a small stream of water. A sapling is a young tree, and a tree is not necessarily a large natural stream of water.