Chemical-company employee: A conservation group's study of the

Chemical-company employee: A conservation group's study of the pollutants released into the environment by 30 small chemical companies reveals that our company and four other companies together account for 60 percent of the total. Clearly, our company releases more pollutants than most chemical companies similar to us in size.

Which one of the following is an assumption required by tbe employee's argument?

(A) The conservation group that produced the study is not hostile to the chemical industry.
(B) The employee's company does not produce chemicals whose processing naturally produces more pollutants than the chemicals produced by other small chemical companies.
(C) The total pollution produced by all small chemical companies combined is not greatly outweighed by that produced by large chemical companies.
(D) The four other companies mentioned by the employee do not together account for very close to 60 percent of the total pollution by the 30 companies.
(E) There is no significant variation in the quantities of pollutants released by the other 25 small chemical companies.

Source: LSAT