Regarding Proper Ethical Guidelines, Which (If Any) of the Following

Multiple Choice

Regarding proper ethical guidelines, which (if any) of the following is correct?

A) The use of client estimates in preparing a return may be acceptable.
B) Under no circumstances should a question on a tax return be left unanswered.
C) If a client has made a mistake in a prior year's return and refuses to correct it, you should withdraw from the engagement.
D) If the exact amount of a deduction is not certain so as to increase the appearance of greater certainty.
E) None of these.