The law of demand is the principle that there is relationship between the price of a good and the quantity buyers are willing to purchase in a defined time period, ceteris paribus.

an inverse,

Explanation:

Inverse relationship refers to a situation when two variables will always go to the opposite direction.  Let's say that there are variable A and variable B. In an inverse relationship, when the amount of Variable A increase, the amount of of Variable B will decrease.

This is what happen within relationship between price and quantity of goods purchased.

When the price of the product increased, there will be Less people who can afford it and choose to find substitute product. This will lead to lesser demand and  a decrease in total quantity of goods purchased.

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."

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explanation:

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