Is when one allele completely masks another.

complete dominance

incomplete dominance

codominance

none of the above

Complete dominance

Explanation:

Complete dominance is a condition where the allelic configuration remains in an hetrozygous condition. Out of the pair of alleles the one allele is typically dominant over the other. The other one remains recessive. The allele which is dominant get expressed in a trait and mask the effect of the recessive allele.  

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.

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.