存著再看年 06:50 会员 Economic models | Basic economics concepts | AP Macroeconomics and Microeconomics | Khan Academy
存著再看年 01:14:42 Smithsonian美国艺术馆 Eldredge Prize: Maurie D. McInnis “Slaves Waiting for Sale: Visualizing the American Slave Trade”
存著再看年 12:20 选择类别 Enols and Enolates – Reactivity, Halogenation, and Alkylation: Crash Course Organic Chemistry #43