3 - Exposure to radiation
Radiation ionises cells and can cause mutations in genes.
The rest of the options have no affect on genetics at all, merely a temporary affect on the physical aspects of the body, such as heart rate etc.
Answer:
I think the answer me if I'm wrong I'm very very sorry.
Answer:
drill rigs use more diesel fuel instead of coal
Answer:
I think B because white blood cells fight off bacteria and stuff. I hope this is right for you! if not I am sorry! Have a great holiday.