Growth is synonymous with reproduction for which of the following organisms?

The correct option is All of the above.

In biology, the relationship between growth and reproduction depends significantly on the complexity of the organism:
1. Multicellular Organisms: In multicellular organisms, growth (an increase in body mass or size through cell division) and reproduction (the production of offspring) are distinct, mutually exclusive processes.
2. Unicellular Organisms: In single-celled (unicellular) organisms, the entire body consists of a single cell. When a unicellular organism undergoes cell division, it increases the number of cells, which is defined as growth, while simultaneously creating new individuals, which is reproduction. Consequently, for these organisms, growth and reproduction are synonymous terms.

Let us analyze the given options:
- Unicellular algae: These are single-celled eukaryotic organisms that reproduce and grow through simple cell division.
- Amoeba: Amoeba is a unicellular protozoan that reproduces mainly via binary fission, where one cell divides to become two new individuals.
- Bacteria: Bacteria are unicellular prokaryotic microorganisms that multiply and grow through binary fission.
Because all of these organisms are single-celled, growth is synonymous with reproduction for each of them. Therefore, the correct choice is "All of the above".