单项选择题

China lies mainly in the northern temperate zone under the influence of monsoon(季风). From September and October to March and April next year monsoon blow from Siberia and the Mongolia Plateau into China and decrease in force as it goes southward, causing dry and cold winter in the country and a temperature difference of 40℃ between the north and south. The temperature in China is 5℃ to 18℃ lower than that in other countries on the same latitude in winter. Monsoon blows into China from the ocean in summer, bringing warm and wet currents, thus rain.
Great differences in climate are found from region to region owing to China’s extensive territory and complex topography(地形). The northern part of Heilongjiang Province in northeast China has no summer, Hainan Island has a long summer but no winter; the Huaihe River valley features four clear seasons; the western part of the Qinghai-Tibet Plateau is covered by snow all year round; the southern part of the Yunnan-Guizhou Plateau is spring-like all the year; and the northwestern inland region sees a great drop of temperature in the day.
The word "current" in the first paragraph most probably means"______".