— Sorry. I didn't catch it. I ________ about something else.
A:think
B:will think
C:was thinking
D:thinks
如图,△ABC中,下面说法正确的个数是( )个.
①若O是△ABC的外心,∠A=50°,则∠BOC=100°;
②若O是△ABC的内心,∠A=50°,则∠BOC=115°;
③若BC=6,AB+AC=10,则△ABC的面积的最大值是12;
④△ABC的面积是12,周长是16,则其内切圆的半径是1.
生物体生命活动的物质基础是指