What description of dna replication is correct?
a. the two strands of dna separate and restriction enzymes cut up one strand. then the dna uses these pieces to synthesize two new strands out of the old one.
b. the two strands of dna separate, and each one receives a complementary strand of rna. then the new rna strands serve as templates for the assembly of many new dna strands.
c. ligase separates the two strands of the dna double helix. then dna polymerase synthesizes the leading strands and primase synthesizes the lagging strand.
d. helicases separate the two strands of the double helix, and dna polymerases use each of the original strands as templates to create two new strands.

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.