Concept:A living organism is any individual life form that can carry out all basic life functions independently, such as nutrition, respiration, growth, and reproduction.
Explanation:First, examine each option against this definition.
Muscle is a specialized tissue made of cells, but it cannot live or function independently as a whole organism.
A nucleus is a membrane-bound organelle found inside eukaryotic cells; it controls cell activities but is not an organism by itself.
A mitochondrion is also an organelle, known as the powerhouse of the cell; it produces energy but depends on the cell and cannot survive alone.
Yeast, however, is a unicellular fungus.
It is composed of a single cell that performs all life processes, including respiration, reproduction, and metabolism.
Therefore, yeast is a complete living organism.
Answer:C. Yeast