Which best explains why all of the Earth’s freshwater is not available for human use?

2.5% of the earth's fresh water is unavailable: locked up in glaciers, polar ice caps, atmosphere, and soil; highly polluted; or lies too far under the earth's surface to be extracted at an affordable cost.

Explanation:

99% of liquid freshwater on Earth is Stored as Ground water

Much of it probably isn't accessible to us Human.

About 71 % of Earth is covered in water, and the Ocean holds most of it but this is salt water, almost all fresh water is stored underground

d. in sexual reproduction, offspring have more chromosomes than

either parent.

asexual reproduction results in offspring which are genetically the same as the parent organism (not counting a rare mutation). sexual reproduction produces a random mixture of the genetics derived from both parents

explanation:

the tricuspid valve is present between right atrium and right ventricle