Mutation theory was proposed by A. Hugo de VriesB. Gregor MendelC. LamrachD. Kolreuter

The correct answer is: A. Hugo de Vries

Detailed explanation:

Mutation theory was proposed by the Dutch botanist Hugo de Vries in the early 20th century. He conducted experiments on the evening primrose plant (Oenothera lamarckiana) and observed sudden, large, and inheritable variations, which he called "mutations." De Vries suggested that these mutations were responsible for the evolution of new species, thereby providing an alternative to Darwin’s theory of gradualism.

Hugo de Vries's mutation theory highlighted the following points:

Mutations are sudden changes in the genetic material that result in new traits.
These mutations are inheritable and can lead to the development of new species over time.
Evolution occurs in large steps through these mutations, as opposed to gradual, small changes suggested by Darwin.
The other options are incorrect because:

Gregor Mendel is known as the father of genetics for his work on inheritance patterns in pea plants.
Jean-Baptiste Lamarck is associated with the theory of inheritance of acquired characteristics.
Joseph Gottlieb Kölreuter contributed to early studies in hybridization and plant reproduction but did not propose mutation theory.