The correct option is C A. V. Leeuwenhoek
Anton Van Leeuwenhoek first discovered free-living algae Spirogyra cells in water in the pond in 1674 with the improved microscope. The living cells were first discovered by Antony Van Leeuwenhoek. He observed living cells and called them ‘animalcules’. Some small ‘animalcules’ are now called bacteria. The invention of the microscope supported the study of finer details of a living cell.