Why are human beings considered as the most important part of human environment?

Because without humans, there would be no human environment

there are no options provided but you can choose among the following gender-neutral pronouns: zir, hir, eir, vis, tem, eir.

in the normal course of maintaining a pronoun-antecedent agreement, we could have used the words his or her but since we are also required to use gender-neutral language, we need to replace it with its equivalent gender-neutral pronoun.

it all depends on how long the hours are. i think they wouldn't approve of it. in my opinion.