What Should Be a Major Focus in a Teaching Plan $\degree$

What should be a major focus in a teaching plan for a teenager with sickle cell anemia?

A) Limit tobacco use to no more than two cigarettes a day.
B) Eat foods high in iron and vitamin B.
C) Maintain environmental temperature at 65 $\degree$ F to 68 $\degree$ F.
D) Maintain adequate hydration.