The picture below shows a farmer's plastic shed in northern China. The windbreak wall is mainly to prevent the winter wind from damaging the greenhouse. According to the principle of thermal cycle, this kind of work is inferred. C

Analysis of test questions: the winter wind in northern China is northwest monsoon, and the wind-proof wall in the picture should be located at the northwest side of plastic greenhouse. Because of the heat preservation function, the temperature of plastic greenhouse is higher than that outside the greenhouse. According to the principle of thermal cycle, when the working door is opened, the airflow flows from the outside of the greenhouse to the inside, that is, from northeast to southwest. Considering the geostrophic deviation of the northern hemisphere to the right, the horizontal airflow at the threshold flows westward, and item C is correct.