Photo taken on Dec. 7, 2021 shows farmers maintaining strawberries in greenhouse in Gu'an County of north China's Hebei Province. Heated greenhouse are built to extend growing season as the winter deepens. (Men Congshuo/Guangming Picture)

Photo taken on Dec. 7, 2021 shows farmers maintaining strawberries in greenhouse in Gu'an County of north China's Hebei Province. Heated greenhouse are built to extend growing season as the winter deepens. (Men Congshuo/Guangming Picture)

来源：GMW.cn