​Which of the Following Relationships Is Not a Functional Relationship

Multiple Choice

​Which of the following relationships is not a functional relationship? ​

A) ​The cost of rst class postage is determined by the weight of the package.
B) ​The amount of a particular drug in the blood stream is determined by the length of time since the drug had been administered.
C) ​The amount of sales tax one pays on a durable good is determined by the cost of the durable good.
D) ​The cost of purchasing a particular pattern of new carpet is determined by the area of carpet that is purchased.
E) ​The number of hours a college student studies per week is determined by the amount of tuition she pays out of pocket.