EXPLANATION
As we can see in the picture, there is a proportional relationship between the bottles that are thrown away each month and those recycled.
Considering two ordered pairs as for instance, (x_1,y_1)= (40,12) and (x_2,y_2)= (50,15) give us the appropiate rate.
[tex]\text{rate}=\frac{y_2-y_1}{x_1-x_1}[/tex]The rate is as follows:
[tex]rate=\frac{(15-12)}{(50-40)}=\frac{3}{10}\frac{bottles\text{ recycled}}{\text{bottles thrown away}}[/tex]In conclusion, for each 10 bottles thrown away, there are 3 bottles recycled.
The answer is the option B.