I think the first one because if the infection is severe, you want a higher dosage, hopefully this is correct
Individuals need to adjust their physical activity to account for reduced flexibility, a loss of balance, as well as decreased energy levels as they age. As we see, there is a number of rather unwanted changes which happen with old age so the correct answer would be D - all of the above.
I think it’s b because it helps the blood cells enable more oxygen and takes it to the muscles
Hope that help
