What is the normal oral temperature range for an adult?

• A. 96.0-97.5°F (35.6°C to 36.4°C)
• B. 99.5-100.5°F (37.5°C to 38.1°C)
• C. 95.0-96.0°F (35.0°C to 35.6°C)
• D. 97.8-99.1°F (36.5°C to 37.3°C)

Answer: (D)

Normal oral temperature in adults is about 97.8°F to 99.1°F (36.5°C to 37.3°C). This range is what you’d expect when a thermometer is placed under the tongue with the mouth closed, under typical conditions (not right after eating, drinking hot or cold substances, or smoking). Small daily fluctuations are normal, but readings outside this window suggest something outside the usual baseline: higher values may indicate fever (often above about 100.4°F/38°C), while lower values can indicate hypothermia (below about 95°F/35°C). Among the options, the range that matches this normal window is 97.8–99.1°F. The other ranges are either lower than normal or higher than normal for an oral measurement.