B. The snow line at the south slope A in the picture is low, and it is a windward slope with more precipitation, which does not meet the meaning of the question;
C. According to the analysis of the position of this mountain, the slope A in the picture is relatively high, with sufficient heat and rich natural zones, so it is the south slope, and the snow line of the south slope A is low, which is a windward slope with a lot of precipitation, so it is correct;
D. According to the position analysis of this mountain, the A slope in the map is relatively high, with sufficient heat and rich natural zones, so it is the southern slope, the sunny slope and the northern slope, which does not meet the meaning of the question.
So choose: C.