The correct answer is option 'b) Assimilation'.

Explanation:
Assimilation refers to the process through which a young child relates something he sees to something he already knows. It is one of the key concepts in Jean Piaget's theory of cognitive development. Piaget believed that children construct their understanding of the world through a series of stages, and assimilation is a major part of this process.

- Assimilation and Accommodation:
Assimilation and accommodation are two complementary processes that work together in Piaget's theory. While assimilation involves incorporating new information into existing knowledge, accommodation involves modifying existing knowledge to fit new information. Both processes are important for cognitive development.

- Example of Assimilation:
To understand assimilation better, let's consider an example. Imagine a young child who has only seen dogs with short fur. One day, the child sees a dog with long fur. The child's existing knowledge about dogs includes the idea that they have short fur. However, instead of rejecting the new information or creating a completely new category for dogs with long fur, the child assimilates this new information by incorporating it into the existing category of dogs.

- Importance of Assimilation:
Assimilation is an important cognitive process because it allows children to make sense of their experiences and build upon their existing knowledge. It helps children create mental schemas or frameworks that they can use to understand and interpret new information. Without assimilation, children would struggle to make connections between new and existing knowledge, hindering their cognitive development.

- Limitations of Assimilation:
While assimilation is a fundamental process in cognitive development, it has its limitations. Sometimes, new information cannot be easily assimilated into existing knowledge, leading to a state of cognitive disequilibrium. In such cases, accommodation becomes necessary to modify existing knowledge and create a new understanding of the world.

In conclusion, assimilation is the process through which a young child relates something he sees to something he already knows. It is a vital part of cognitive development and helps children make sense of their experiences by incorporating new information into their existing knowledge.