"D" is correct... in a function, if we have a finite number of values in the domain....each of these will be paired with some y value....
"A" has a finite domain, but not an "infinite" cost [ infinite range]....the cost depends upon the number of minutes but it is never greater than 100m ....where m represents the cost per minute
"B" has some finite domain domain ..... but also a finite range of $100
"C" has some finite domain and range [ we assume that there are not an infinite number of minutes in each billing cycle....!!!!!]