A scientist investigated the effect of changes in external temperature on a person’s internal body temperature - Edexcel - GCSE Biology - Question 5 - 2012 - Paper 1

From the graph,

• At an external temperature of 20 °C, the internal body temperature is 37.4 °C.
• At an external temperature of 40 °C, the internal body temperature is 37.8 °C.

To find the difference:

$ext{Difference} = 37.8 °C - 37.4 °C = 0.4 °C$

Thus, the difference in internal body temperature is 0.4 °C.