Which scientist encouraged Frankenstein to pursue the study of natural sciences, which he had previously abandoned?

A. M. Krempe

B. Magnus

C. Paracelsus

D. Waldman

It is destiny that causes him to meet M. Waldman, who develops Victor's passion for the natural sciences of galvanism, electromagnetism, and alchemy. Victor might have been a good mathematician, if he were devoid of passion. But his passion causes him to pursue his dreams and the God-like ideal, and so he seeks intuitively to seek the answers to stopping death through the life sciences.

So yeah the answer would be the D. Waldman.