Regarding proper ethical accounting guidelines, which, if any, of the following is correct? a. If the exact amount of a deduction is not certain (e.g., around mid-$600s), it should be recorded as an odd amount (i.e., $649) so as to increase the appearance of greater certainty. b. Under no circumstances should a question on a tax return be left unanswered. c. The use of client estimates in preparing a return may be acceptable. d. If a client has made a mistake in a prior year's return and refuses to correct it, the accountant should withdraw from the engagement. e. None of these choices are correct