Which of the following describes a mutual relationship? A pack of hyenas hunt together so they can attack larger animals.
Ants drink nectar from an acacia tree and protect the tree from harmful insects.
A flock of seagulls fly together to reduce the amount of air resistance they feel.
A grasshopper and a rabbit eat different types of plants to avoid competition.

prism b but im not for sure

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.

links? do you have a link? i don't see anything?