The CPA firm found that net income had been overstated. Which of the following errors could be the cause?

A、Failuretocovertunexpiredinsurancetoinsuranceexpense;
B、Noentrymadetorecordpurchaseoflandforcashonthelastdayoftheyear;
C、Failuretorecordpaymentofanaccountpayableonthelastdayoftheyear;
D、Failuretomakeanadjustingentrytorecordrevenuethathadbeenearnedbutnotyetbilledtocustomers.