Central idea of A thing of beauty

Find the number of selections of one or more things from the group of p identical things of one type, q identical things of another type, r identical things of the third type and n different things.

Which of the following gave the idea of nucless of the atom ?

Which scientist gave the initial idea of survival of the fittest :

Which of the following structure is correctly drawn according to fundamental idea of VSEPR theory?

The idea of mutations was brought forth by

The idea of mutations was brought forth by