How was Mendel's work ultimately reconciled with Darwin's theory of natural selection during the evolutionary synthesis in the 1930s and 1940s?

• A. Scientists recognized that once one thinks about species as populations, rather than individuals, there is no incompatibility between them.
• B. Mendel's theory was replaced by the mutation theory.
• C. It was recognized much of the variation we observe in nature is due to recombination, rather than mutation.
• D. A and C.