Why is secondary treatment often needed for sewage?
A) The dissolved organics are too high and lead to bacterial growth.
B) The solution is contaminated with dangerous bacteria.
C) There are too many dissolved inorganic compounds.
D) There are too many finely divided particles that need to be filtered.
E) none of the above
Question 2
Earth's gravitational force is incapable of keeping the atmospheric helium from escaping into space.
Indicate whether the statement is true or false