Option A. is a function...
here For different values of x in Domain of(x,y) ;There is a unique image y in codomain.
All others have more than one image for a single value x.
Hope it helps...
Regards;
Leukoniv/Olegion.
Answer:

Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form
or 
we have the points (2,14) and (4,28)
Find out the constant of proportionality k
For (2,14) ----> 
For (4,28) ----> 
so
the value of
therefore
The equation is
I think the answer is 5 because 25 divided by 5=5
5 = 50
8 = 80
because:
20:2= 10 so 1 shirt will collect 10