Darwin,in his 'Natural Selection Theory',did not believe in any role of which one of the following in organic evolution?

The Darwinian variations are

According to $Darwin$,fitness refers to .........

Given below are two statements regarding evolution.
Statement-$I$: Natural selection is the establishment of a phenotypic trait in changing environmental conditions.
Statement-$II$: Natural selection encourages those genes or traits that ensure highest degree of adaptive efficiency between population and its environment.
In the light of above statements, choose the most appropriate answer from the options given below.

Natural selection where more individuals acquire specific character value other than the mean character value,leads to:

Which of the following can be used as an illustration to demonstrate the process of evolution in animals?