Answer:
B. the combination of modern genetics and Darwinism.
Step-by-step explanation:
The modern synthesis refers to the concept which combined the theory of inheritance by Mendel and theory of evolution by Charles Darwin. The theory also used the concept of Theory of germplasm.
The modern synthesis concept came in the early 20th century when the studies were going on Mendel's theory and the evolutionary aspects. The concept led to the formation of new concepts like the macroevolution, microevolution and the evolution affected by mutation of genes.
Thus, Option-B is correct.