Trees, birds, and bacteria are all similar because they are all formed from — A. Cells that carry out similar life functions present in all cells. B. Tissues that absorb energy from sunlight. C. Spontaneous generation of life. D. The fixation of nitrogen in the air into protein molecules.

A. Cells that carry out similar life functions present in all cells.

Explanation:

A cell can be defined as the structural, fundamental, biological and functional unit of life. Cells are found in all living organisms because they are the basic unit of life.

A unicellular organism refers to a living organism that possess a single-cell while a multicellular organism has many (multiple) cells.

Generally, cells have the ability to independently replicate themselves.

In a cell, the "workers" that perform various functions or tasks for the survival of the living organism are referred to as organelles.

Some examples of cell organelles found in all living organisms such as trees, birds, and bacteria include;

1. Nucleus: it controls all the activities taking place in the cell and the synthesis of proteins.

2. Mitochondria: it provides all the energy required in the cell by transforming energy forms.

3. Lysosomes: they are responsible for absorbing materials and breaking the materials taken in by the cells.

4. Chromosomes: they give sets of instructions for the synthesis of products.

5. Ribosomes: they are involved in the build up of proteins.

6. Endoplasmic Reticulum: this is where the ribosomes perform their tasks.

7. Cytoskeleton: they help to maintain and support the shape of the cells.

8. Vesicles: they ensure proteins are properly transported to the right and exact location.

9. Golgi apparatus: it prepares the protein for export by chemically tagging them.

10. Cell membrane: is the wall of the cell and typically controls what leaves and enters the cell.

Hence, trees, birds, and bacteria are all similar because they are all formed from cells that carry out similar life functions present in all cells.