A.
contracts to move substances through the body
D.
breaks down food to acquire nutrients
Its stabilising. Since the selection pressure is against the extremes which are the normal blood and the sickle cell anaemia.
The fertilizers used by farmers can have negative effects on aquatic ecosystems because there is every possibility that the runoffs from the fields can create an algal bloom in the nearby water body. This algal bloom can have a very negative effect on the living organisms of the aquatic body. I hope it helps.
