The graph illustrates the number of deaths caused by MRSA infection per $100\,000$ people in a population of over-65-year-olds from 2005 to 2012. Suggest one possible reason for the pattern shown in the graph.
- Aa decrease in the size of the population of over-65-year-olds
- Bantibiotics do not affect viruses
- Cmore effective antibiotics are being used to treat infected people
- Dover-65-year-olds are immune to MRSA infection