Query: When did Hu Yaobang visit Tibet?
Context: In 1980, General Secretary and reformist Hu Yaobang visited Tibet and ushered in a period of social, political, and economic liberalization. At the end of the decade, however, analogously to the Tiananmen Square protests of 1989, monks in the Drepung and Sera monasteries started protesting for independence, and so the government halted reforms and started an anti-separatist campaign.