Who coined the phrase 'Survival of the Fittest'?

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:

Which of the following is associated with evolution?

The replica plating experiment was performed to prove which of the following concepts?

$XX$ is a type of selection process in evolution. $XX$ promotes population changes in one particular direction. $XX$ favours small or large-sized individuals,and the mean size of the population changes in $XX$. Identify $XX$.

Evolution that shifts the allele frequency in a consistent direction is called?