AP BIOLOGY

Detailed explanation-1: -The correct option is B A cell. Cell is the smallest structural and functional unit of an organism. Each cell of an organism performs functions such as nutrition, transport, excretion and reproduction.

Detailed explanation-2: -A cell is capable of carrying out all life processes, such as nutrition, excretion, respiration, etc. Hence it is called as the functional unit of life. The cell is the smallest unit of life and all the living beings are made up of cells. Hence a cell is called the structural unit of life.

Detailed explanation-3: -The cell is the smallest structural and functional unit of living organisms, which can exist on its own. Therefore, it is sometimes called the building block of life. Some organisms, such as bacteria or yeast, are unicellular-consisting only of a single cell-while others, for instance, mammalians, are multicellular.

Detailed explanation-4: -A cell is the smallest independently functioning unit of a living organism. Even bacteria, which are extremely small, independently-living organisms, have a cellular structure. Each bacterium is a single cell.