Context: The map below shows air temperatures in the lower atmosphere on April 15, 2017. The outlined area shows an air mass that influenced weather in North America on that day.
Look at the map. Then, answer the question below.
Data source: United States National Oceanic and Atmospheric Administration/Earth System Research Laboratory, Physical Sciences Division
Which air temperature was measured within the outlined area shown?
A. 23°C
B. 12°C
C. -23°C
Select the correct answer from the provided options and reply with the letter associated with it.

C