Final answer:
Fritz Zernike invented the phase contrast microscope to study colorless and transparent biological matter. Dutch physicist and Nobel laureate, Zernike's invention enabled detailed observation of living cells. option d is correct.
Step-by-step explanation:
The phase contrast microscope, which is a vital tool for studying colorless and transparent biological matter, was invented by the Dutch physicist Fritz Zernike. This invention has greatly enhanced our ability to observe living cells and microorganisms without staining, which can sometimes kill or alter the sample. He was awarded the Nobel Prize for Physics in 1953 for this significant contribution to the field of microscopy.
Anton van Leeuwenhoek is known as a pioneer in the field of microscopy. His work with microscope lenses led to the discovery of bacteria and protozoa — which he famously called "animalcules." Van Leeuwenhoek's observations, including the movements of single-celled organisms and sperm, laid the foundation for the field of microbiology.