Answer:
Option B). (6,8),(0,0),(18,24) 
Explanation:
The options of the question are
A). (2,4),(0,2),(3,9) 
B). (6,8),(0,0),(18,24) 
C). (3,6),(4,8),(9,4) 
D). (1,1),(2,1),(3,3)
we know that
A relationship between two variables, x, and y, represent a proportional variation if it can be expressed in the form 
 or
 or 
 
 
In a proportional relationship the constant of proportionality k is equal to the slope m of the line and the line passes through the origin 
Verify each case
case A) (2,4),(0,2),(3,9) 
This set of points not represent a proportional relationship because in a proportional relationship the intercepts must be equal to (0,0) and this set of points have the point (0,2)
case B) (6,8),(0,0),(18,24) 
Find the constant of proportionality k

For x=6, y=8 ----> 

For x=18, y=24 ----> 

The line passes through the origin
The linear equation is 

so
This set of points could be n the line that Sara graphs
case C)  (3,6),(4,8),(9,4) 
Find the constant of proportionality k

For x=3, y=6 ----> 

For x=4, y=8 ----> 

For x=9, y=4 ----> 

The values of k are different
therefore
This set of points not represent a proportional relationship
case D) (1,1),(2,1),(3,3)
Find the constant of proportionality k

For x=1, y=1 ----> 

For x=2, y=1 ----> 

The values of k are different
therefore
This set of points not represent a proportional relationship