Choice "D" is correct. This statement is incorrect. Under the SEC's rules, the lead and concurring partner must rotate off the engagement after five years and other audit partners must rotate after seven years. (Note that the IFAC Code of Ethics requires that the lead and engagement quality review partners on public company audits rotate after no more than seven years.)
Choice "b" is incorrect. This statement is correct. Small firms with fewer than five clients who are issuers may be exempted from the partner rotation rules.
Choices "a" and "c" are incorrect. These statements are correct. The lead and concurring partners are subject to a 5 year time out period before they can return to an engagement. Other audit partners are subject to a two year time out period.