Hillary Is a Cash-Basis Calendar-Year Taxpayer

Hillary is a cash-basis calendar-year taxpayer. During the last week of December she received a letter containing a $5,000 check for services. Which of the following is a true statement?

A) Hillary is taxed on the $5,000 of service income in the year she cashes the check.
B) Hillary is taxed on the $5,000 of service income in the year the check was mailed.
C) Hillary is taxed on the $5,000 of service income in the year she receives the check.
D) Hillary is taxed on the $5,000 of service income in the year she provides the services.
E) None of these is true.