Question

which scientific instrument helped scientists develop the cell theory? a 3d printer - it helped scientists create new kinds of plants. b microscope - it made it possible to see unicellular organisms and cells that were invisible to the naked eye. c telescope - it allowed scientists to see that planets are made of cells. d thermometer - it was used to measure temperature changes in living things.

Explanation:

The cell theory was developed based on the observation of cells. Microscopes made it possible to see cells that were invisible to the naked - eye, including unicellular organisms. This was crucial for the development of the cell theory. 3D printers are not related to cell - theory development. Telescopes are for observing celestial objects, not cells. Thermometers measure temperature and have no direct link to cell - theory development.

Answer:

B. Microscope - It made it possible to see unicellular organisms and cells that were invisible to the naked eye.