Final answer:
The management representation letter should cover the period from d) January 1, 2011 through May 1, 2012.
Step-by-step explanation:
The management representation letter should cover the period from January 1, 2011 through May 1, 2012. This is because Key Co.'s current management team was not present until January 1, 2011, so they are responsible for the financial statements from that point forward.
The audit report is being issued on May 1, 2012, so the management representation letter should cover the period up until that date.