Answer:
A & B are both correct
Step-by-step explanation:
Too little nutrients available will limit the amount of producers and lead to smaller food chains because if you don't have enough nutrients to sustain producers, producers are backbone of foodchains hence not enough producers will survive and this will lead to smaller food chains.
Too much nutrient available can lead to eutrophication and damage the ecosystem, this is very true because if you have ever heard of algal blooms or seen like green layer covering large amounts of water, those areas are full of algaes and they are taking it alot of O2 in water thus depriving the organisms and plants nearby of O2 and essentially killing them.