Answer: The correct answer is- D. 20ºC
Average can be described as a central value in the given set of observation that can be mathematically calculated.
It is the sum total of all the values / set of measurements in a given data divided by the total number of observations.
Thus, for the given set of measurements, average is calculated as-
Average= [27⁰C+ 12⁰C+ 31⁰C + 19⁰C+ 23⁰C+ 11⁰C+ 17⁰C] /7
= 20ºC