What does gene versions mean?

Basically, Its like a  Different version of a gene which are called alleles. Alleles are described as either dominant or recessive depending on their associated traits

Explanation:

These gene variants still code for the same trait (i.e. hair color), but they differ in how the trait is expressed (i.e. brown vs blonde hair). Different versions of the same gene are called alleles. Genes can have two or more possible alleles. Individual humans have two alleles, or versions, of every gene.

Explanation:

b.have there own function.

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.