He dropped out of school at an early age. Now he ____(feel sorry) doing that.
设a=0.60.6,b=0.61.5,c=1.50.6,则a,b,c的大小关系是( )
①(a+b)×63g ②(a+b)×189g ③(a+b)mol ④Vc﹣9a+b/3)mol.