What Was the Perceived Fundamental Conflict Between Darwin's and Mendel's

What was the perceived fundamental conflict between Darwin's and Mendel's theories?

A) Darwin was a scientist while Mendel was a monk.
B) Mendel's experiments were unbiased, while Darwin set out to prove evolution by natural selection.
C) Mendel's experiments were based on simple traits while Darwin's evidence was based on complex characteristics.
D) Mendel's theory was based on experimentation while Darwin's was based on observation.