What is the Caste system and how has it changed in recent past?

Test 5B covers AsiaCentral AsiaRussia and its impact on Geopolitics……..how China impacts Tibet………the concern if lake level in Central AsiaEast AsiaChina’s [population polices pros and cons…..position of women in Japan compared to other industrialized countries……Impact of major Dam building in China /pros and cons……..China and Japan’s similarities and differences on impact on global cultureSouth Asia different regions of geopolitical and ethnic tension within South Asia……pros and cons of Green Revolution on South Asia’s food supplies…….what is the Caste system and how has it changed in recent past…….South East Asiawhy is there significant deforestation of S.E. Asia and how could it properly be addressed…….impacts negatively or positively on transmigration [solve or aggravate the population problem]…….understand causes of wide scale air pollution in S.E. Asia………look at the 3 types major types of agriculture in the region [Sweden/Plantation and Cultivation]