Choice "A" is correct. An auditor would most likely inquire as to whether any unusual adjustments were made after year-end that would require adjustment to and/or disclosure in the year-end financial statements.
Choice "c" is incorrect. Obtaining evidence about A/R that were established after year-end would not provide the auditor with information about subsequent events, since any information about these A/R would not require adjustment to or disclosure in the prior year financial statements.
Choice "b" is incorrect. Comparing the financial statements being reported on with those of the prior period is not a very good source of subsequent event information.
Choice "d" is incorrect. Changes in accounting personnel at any time would probably not result in any subsequent event financial statement adjustment or disclosure.