Answer:
D. Several cells are in the process of dividing into two new cells
Step-by-step explanation:
The universal cell theory which was proposed in 1838 and contributed by three scientists namely: Theodor Schwann, Rudolf Virchow, and Mathias Schleiden, consists of three components namely:
1) Cell is the basic and functional unit of life
2) All living organisms are made up of one or more cells.
3) All existing cells arise from pre-existing cells.
Hence, in this question involving a scientist who is observing living Cells in a Petri Dish under a Compound Light Microscope, the observation that "Several cells are in the process of dividing into two new cells" provides evidence to support one of the three components of the cell theory ( all living cells arise from preexisting cells).