Final answer:
Air tissue is not a tissue of a flowering plant. Flowering plants have dermal, vascular, ground, and meristematic tissues. The slide of parenchyma represents a simple tissue. The correct option is 3.
Step-by-step explanation:
The tissue that is not one of the tissues of a flowering plant among the choices provided is air tissue. Flowering plants have dermal tissue (the outer protective layer), vascular tissue (which includes the xylem and phloem for transporting water, minerals, and nutrients), ground tissue (which is responsible for photosynthesis and storage), and meristem (regions of active cell division).
Regarding the plant biologist examining sections of plant tissue under the microscope, the slide that is a sample of a simple tissue is the one showing parenchyma with only one type of cell.