Xinjiang is a typical temperate continental climate, which is mainly manifested in the annual and daily changes of temperature. Compared with other regions in the same latitude in the world, the temperature is obviously lower in winter and higher in summer. Therefore, b does not meet the meaning of the question;
C, Northwest China is located inland, the temperature changes dramatically, and the annual precipitation decreases from east to west. Generally speaking, drought is the main feature of the natural environment in this area, so C does not meet the meaning of the question;
D. Xinjiang's topography is dominated by basins and mountains, characterized by three mountains and two basins, from north to south: Altai Mountain, Junggar Basin, Tianshan Mountain, Tarim Basin and Kunlun Mountain.
So choose: a.