Auditors perform a key function in business: not only are the validity and reliability of financial statements needed to be ascertained by them, but also on performing assessments of a company's internal control.

(A) not only are the validity and reliability of financial statements needed to be ascertained by them, but also on performing
(B) they not only ascertain the validity and reliability of financial statements for public use, but also perform
(C) the validity and reliability of financial statements not only needs to be ascertained by them, but also they perform
(D) not only the validity and reliability of financial statements need to be ascertained by them, but also on performing
(E) the validity and reliability needs to be ascertained not only on financial statements, but also they perform