Option a is correct because cells are the structural and the functional part if the body. The cells are just like building made up of bricks.

Cell as the Structural and Functional Unit of Living Beings

Cells are the basic structural and functional units of all living organisms. They are the building blocks of life and perform various essential functions necessary for the survival of an organism.

Structural Unit

- Cells are responsible for maintaining the structure of an organism. They are specialized to perform specific functions depending on their type, such as nerve cells for transmitting signals or muscle cells for movement.
- Different types of cells come together to form tissues, which further combine to create organs and organ systems. This hierarchical organization is crucial for the proper functioning of an organism.

Functional Unit

- Cells carry out various functions necessary for life, such as metabolism, growth, reproduction, and response to stimuli. Each cell has specific organelles that perform different functions, such as the nucleus for genetic information, mitochondria for energy production, and ribosomes for protein synthesis.
- Cells communicate with each other through chemical signals to coordinate their activities and maintain homeostasis within the organism. This communication is vital for the overall functioning of the organism.

Conclusion

In conclusion, cells are the structural and functional units of all living beings. They play a crucial role in maintaining the organization and function of an organism. Understanding the importance of cells is essential for studying biology and gaining insights into the complexity of life processes.