A Client's Axillary Temperature Is 100

A client's axillary temperature is 100.8°F (38.2°C) . The nurse realizes that this is outside the normal range for this client and that axillary temperatures do not reflect the core temperature. What should the nurse do to obtain a good estimate of the core temperature?

A) Add 1°F to 100.8°F to obtain an oral equivalent.
B) Add 2°F to 100.8°F to obtain a rectal equivalent.
C) Obtain a rectal temperature reading.
D) Obtain a tympanic membrane reading.