The correct answer is: A. Child : School

A river is a large natural stream of water flowing in a channel to the sea, a lake, or another river. An ocean is a large body of salt water that covers much of the Earth's surface. A child is a young human being below the age of puberty. A school is an institution where children are educated.

A child is to a school as a river is to an ocean. A child goes to school to learn and grow, just as a river flows to the ocean to become larger and more powerful. Both a child and a river are essential parts of the natural world, and both play an important role in our lives.

The other options are incorrect because they do not accurately reflect the relationship between a river and an ocean. A book is not to a library as a river is to an ocean. A book is a collection of written or printed material, whereas a library is a building or room where books are kept for people to read. A lane is not to a road as a river is to an ocean. A lane is a narrow road, whereas a road is a wider path that is used for transportation. Cloth is not to a body as a river is to an ocean. Cloth is a material that is used to make clothes, whereas a body is the physical structure of a person or animal.