The invention of microwave oven was inspired by which of the following?

Radar During World War II (1945), Spencer, an American radar engineer, happened to find the chocolate bar in his pocket melted and sticky when he was doing radar experiments. He suspected that it was caused by his body temperature, and later he found the thermal effect of microwave in continuous experiments. Using this thermal effect, the United States issued a 1 patent on microwave in 1945, and Raytheon Company of the United States developed the world's first 1 microwave oven in 1947. In the 1940s, microwave ovens were mainly used in industry and commerce.