Jackals is the main subject of the sentence
40 days are important because:-
Grade wise:- If you were to miss out on 40 days of classes, it would bring you very behind in your classes. Your grades would drop tremendously and you would get stressed.
Health wise:- If you dont brush your teeth for 40 days, or even go off your diet for 40 days, your health would be in danger. YOU NEED TO BRUSH YOUR TEETH AT LEAST TWICE EACH DAY!! Also, make sure you keep a balanced diet. :)
A paediatrician (child doctor)
Reading is important so that we can write down the illness or log things into a computer or so that we can give dosages of medicine.