Anemia can be caused by a great amount of things. The most common reason is through iron deficiency, which is linked to other illnesses that cause anemia. Or, through malnutrition where the patient is not getting the right amount of vitamins or minerals in their diet. The protein hemoglobin contains iron, which is why the hemoglobin levels drop at times when there is anemia
I would say feelings of worthlessness. You can't really see it on their body, but they can tell you if they choose to, so that makes it hidden in my opinion.
I hope that helps!
The answer would be: A. Absolute method
The absolute method is done, normally, carrying out by calculating the maximum amount of recital that you and your brother could do over an allotted amount of time. For example, in about 1 minute, the person with the alternative recital is more likely the one with more muscle endurance.