Random genetic drift in a population probably results from

To be evolutionarily successful,a mutation must occur in the

Select the correct pair regarding the population of moths in the $1920$s.

Given below are two statements regarding evolution.
$Statement-I$: Selection against harmful mutation leads to a mutation balance.
$Statement-II$: In mutation balance, the allele frequency of harmful recessives keep on changing generation after generation.
In the light of above statements, choose the most appropriate answer from the options given below:

What is genetic drift a change in?

Hugo de Vries worked on which organism?