Who is Antoni van Leeuwenhoek?

• A. He discovered the structure of DNA
• B. He discovered both protists and bacteria, advancing microscopy
• C. He formulated the theory of natural selection
• D. He invented the electron microscope

Answer: (B)

Antoni van Leeuwenhoek is celebrated for expanding our view of life by making and using powerful simple microscopes to reveal a hidden world. He was the first to observe and describe microorganisms—both protists and bacteria—when he looked at pond water and dental plaque. These observations showed that many forms of life exist unseen to the naked eye and demonstrated how powerful microscopy can be for studying biology. His work laid the foundation for microbiology and transformed our understanding of living systems at the smallest scales.

The other claims don’t fit with what he accomplished: the structure of DNA was discovered much later by scientists like Watson and Crick; natural selection was proposed by Darwin; the electron microscope was developed long after Leeuwenhoek's time.