A:in line with
B:in reply to
C:in return for
D:in honour of
①若sinAsinB=2sin2C,则0<C< π4 ;
②若a+b>2c,则0<C< π3 ;
③若a4+b4=c4.则△ABC为锐角三角形;
④若(a+b)c<2ab,则C> π2 •
亚马孙雨林被称为地球之肺,原因是( )