Answer:
The correct answer is:
Cell (D.)
Explanation:
The cell is the basic structural, functional and biological unit of a living organism that is the smallest unit of life. It is said to be the building block of life. Being the smallest unit of life, a cell is a collection of organelles and biomolecules that can function independently and still possess the qualities of life. These structures are enclosed in a cytoplasm, within a membrane, and these biomolecules include Nucleic acids (DNA, RNA), proteins etc.