The correct answer is - A. A high-pressure system lingering over an area.
Explanation:
A heatwave is a period of hot weather that is not normal in the region that can last for two or more days. Heatwaves only take place in case of a temperature increase above the average for a particular area in history.
When air trapped in a particular area due to a high-pressure system. The trapped are leads to an increase in the temperature due to sunlight which leads to the heatwave.
