"It's July..." The hottest time of the year has finally arrived. The fan hanging on the ceiling of the classroom is spinning slowly, trying hard to bring some coolness to the more than fifty students below. The summer sun is particularly diligent. It was already scorching the trees on the playground just after eight o'clock in the morning, and the whole teaching building was filled with thick heat. Chen Yili fanned himself with his homework book and looked out the window with squinted eyes. The class bell rang soon. It was so hot. How could I attend the class?