I posted this earlier but received no response. It's a tough question. Does anyone know a web site I can go to?

Question

It is estimated that industires and sewage treatment facilities discharge into the Chesapeake an amount of waste water equal to _____% of the volume of the bay annually.
a. 5
b. 10
c. 15
d. 20
e. 25

d. 20 %

i had that question before