The correct answer is option 2: 1 and 2.

If a leaky septic tank contaminates the water supply, diseases like cholera and typhoid are likely to spread in the entire community. Let`s look at each option to understand why the correct answer is option 2:

1. Cholera: Cholera is a highly contagious bacterial infection that spreads through contaminated food and water. If the water supply is contaminated by a leaky septic tank, it can lead to the spread of cholera.

2. Typhoid: Typhoid fever is caused by the Salmonella typhi bacteria and is usually transmitted through contaminated food and water. Again, if the water supply is contaminated by a leaky septic tank, it can result in the spread of typhoid.

3. Tuberculosis: Tuberculosis (TB) is primarily an airborne disease, spreading through respiratory droplets when an infected person coughs or sneezes. It is less likely to spread through contaminated water, so option 3 is incorrect.

4. Leprosy: Leprosy, also known as Hansen`s disease, spreads very slowly and mainly through prolonged close contact with an infected individual. It is not likely to spread through contaminated water