Frank recently received a "30-day letter" from the IRS. He does not quite understand the purpose of this letter. Which of the following statements is correct? Question 4Select one: a. The IRS will complete its examination of his tax return in 30 days. b. The IRS is accepting his return as filed and closing the case. c. Frank has exhausted his time to protest the results of the IRS audit and must pay in full within 30 days. d. The IRS is proposing changes to his tax return