Core body temperature is closest to

(A) Rectal [Ganong22-251; 19th*-239/# Rectal temperature is representative of the temperature at the core of the body and varies least with changes in environmental temperature. Oral temperature is normally 0.5 degC lower than the rectal temperature, but it is affected by many factors, including ingestion of hot or cold fluids, gum-chewing, smoking, and mouth breathing.