Define each of the following zones:
a. benthic:
b. pelagic:
c. oceanic:
d. neritic:
e. photic:
f. aphotic:

Benthic Zone-  bottom of ocean

Pelagic Zone- the open ocean that is not near the  coast.

Oceanic zone- Zone that is beyond the continental shelf

Neritic zone- Zone that exists over the continental shelf

Photic zone- Zone where sunlight pass through

Aphotic zone- Zone where sunlight cannot pass through

Explanation:

There two important zones of the  ocean that can be termed as Benthic Zone which lies at bottom of ocean or sea and Pelagic Zone that could be imagined as a cylinder or water column that goes from the surface of the sea or ocean to its bottom. At the very bottom of the sea there lies an ecological region termed as Benthic Zone.The pelagic zone can also be termed as the open-ocean zone and it is in contrast with water that is nearer to the coast or continental shelf.

There are different zones that lies within a Pelagic Zone. They are

Oceanic, Neritic, Photic, Aphotic. The zone that lies beyond the continental shelf comes under this oceanic zone and Photic and Aphotic as the name suggests it refers to light. It referes to the zones where sunlight can penetrate and can not penetrate respectively.

the correct statements are:

the entire length of the human genome is about 3 billion base pairs.

it is divided into 23 pairs of chromosomes that are, 46 chromosomes. 22 pairs are termed as autosomes and 1 pair termed as sex chromosomes (x and y chromosome).  

the study of the human genome can us understand human genetics, genetics of related species as well, and mechanism of certain diseases.