How can you justify that the function shown in the table is linear?

x
16
20
24
28
f(x)
20
15
10
5
a) show that the quotients of corresponding dependent variables are constant for equal intervals of the independent variable.

b) show that the multiples of corresponding dependent variables are constant for equal intervals of the independent variable.

c) show that the differences in corresponding dependent variables are constant for equal intervals of the independent variable.

d) show that the factors of corresponding dependent variables are constant for equal intervals of the independent variable.