Theory of mutation by a De Vries considers that :

The correct option is A Only large mutations take part in developing variations.
Hugo de Vries after his work on Evening Primose, put forth his theory explaining the structural changes in gene structures, called mutation as the cause of variations. Only large, single step and abrupt mutation termed as saltation are capable enough to drive the process of evolution.

So, the correct option is 'Only large mutations take part in developing variations'.