Externalities are a. unintended side-effects. b. always positive, never negative. c. an inevitable by-product of social responsibility. d. a blessing in disguise in inflationary times.

Option a (unintended side-effects) is the right alternative.

Explanation:

A cost, as well as benefit occasioned by such a production company that would not be economically accumulated rather than started receiving by this same producer, seems to be an environmental problem. An externality could be either favorable or unfavorable and therefore can occur whether from the development or use of a particular product. The expenses and rewards may be confidential to a person or an organization, or social, which means that society as a whole should be influenced.

Some other options are given aren't connected to the conclusions reached. So, the obvious response here is just the right one.