A: The difference between the patient's highest and lowest body temperatures is 65438 0.4 degrees Celsius.

(2)39. 1-38.3=0.8(℃),

A: The patient's temperature has risen by 0.8 degrees Celsius.

(3)38-37.7=0.3(℃),

A: At the beginning and end of the day, the patient's temperature was 0.3 degrees Celsius.

(4) From the statistical diagram, how many degrees Celsius is the patient's temperature at 20 o'clock higher than that at 8 o'clock?

38.5-37.8=0.7(℃),

A: The patient's temperature at 20 o'clock is 0.7 degrees Celsius higher than that at 8 o'clock.