Which of the following forces us to make choices?

scarcity
trade-offs
opportunity cost
money

Opportunity cost

Explanation:

Opportunity cost is known to be the benefit an individual would have enjoyed if he or she had done not something else. It is the sacrifice made in choosing between two options when taking decision. For example: choosing between doing homework or watching a programme on television. Thus, if an individual decide to do the homework, watching a programme on television is the alternative forgone which is the opportunity cost.

answer; i believe the correct answer is (4) flip a coin as each participant arrives,heads indicates assignment to the first group: tails indicates assignment to the second group;

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.