economics help?

[hehe]

My educated guess for the following questions are b, d, a
pls correct me

economists view pollution as a textbook example of
a. public goods
b. externalities
c. increasing returns to scale
d. the evils of monopoly

The fat that pollution is often a detrimental eternality suggests that
a. cleaning up the environment must be done by direct government expenditures.
b. without government intervention, profit-maximizing private firms cannot be expeced to clean up the environment.
c. public agencies have been responsible for most of the pollution.
d. direct controls are superior to other forms of government intervention.

Economists typically argue that _______ are likely to be most effective in reducing pollution over the long run.
a. direct controls
b. taxes on emissions
c. voluntary programs
d. specifications as to allowable equipment and/or procedures