Which symbol in the figure is used to represent a thermostat contact for a heating system

Answer:
It should be the A (I may be incorrect)
Explanation:
source: https://www.industrial-electronics.com/Electricity-Refrigeration-Heating-Air-Conditioning_5b.html
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Fig 26 Symbols for heating and cooling thermostats: Heating thermostat; opens on temperature rise; Cooling thermostat; closes on temperature rise
hope that helps