Which one of the following mutations partially or fully reverses the harmful effects of a previous mutation?

Name the scientist who proposed the Mutation Theory.

Hereditary variations in plants have been produced by the use of

What is the mechanism of moving a segment from one linkage group to another called?

Hugo de Vries formulated the "Mutation Theory" based on the experiments he conducted on:

Assertion $(A)$: Mutation results in changes in genotype and phenotype of an organism.
Reason $(R)$: Mutation leads to alteration of $\text{DNA}$ sequences,i.e.,variations in $\text{DNA}$.
Choose the correct answer from the options given below.