如图,△ABC∽△AED,∠ADE=80°,∠A=60°,则∠B等于( )
A:40°
B:60°
C:80°
D:100°
下图为我国某省区植被覆盖度(数值越大,表示植被覆盖状况越好)沿经度变化示意图。图示植被覆盖度经度变化规律的影响因素最主要是( )
— Why didn't you go to the cinema with us that afternoon?
— I______ at the station for my uncle from Beijing.
下列成语反应的历史事件先后顺序,排列正确的是( )
①草木皆兵 ②四面楚歌 ③三顾茅庐 ④投笔从戎
各项均为正数且公差为1的等差数列{an},其前n项和为Sn,则limn→∞Snan·an+1=( )