The correct answer is (b) Darwin.
Explanation: Charles Darwin is credited with the theory of evolution by natural selection, where organisms with advantageous traits in their environment are more likely to survive and reproduce, passing those traits on to their offspring.
Key points about other options:
Mendel:
Gregor Mendel is known for his work on genetics and the laws of inheritance, not evolution by natural selection.
Morgan:
Thomas Hunt Morgan was a geneticist who studied fruit flies and made significant contributions to understanding genetics, but not the theory of natural selection.
Lamarck:
Jean-Baptiste Lamarck proposed a different theory of evolution, known as Lamarckism, which suggested that organisms could acquire traits during their lifetime and pass them on to their offspring, which is now considered incorrect.