Which of the following conditions will contribute to the stability of a gene pool in a natural population?

1. Large population
2. No net mutation
3. Non-random mating
4. No selection

1. $\text{P}$ Only
2. $\text{P}$ and $\text{Q}$  Only
3. $\text{P}$ and $\text{R}$  Only
4. $\text{P},$ $\text{Q}$ and $\text{S}$  Only