①7×(9+12)÷3-2=7×21÷3-2,=49-2,=47;②7×9+12÷(3-2)=7×9+12÷1,=63+12,=75;③(7×9+12)÷3-2C=75÷3-2,=25-2,=23;④7×(9+12÷3)-2=7×13-2,=91-2,=89.23<47<75<89,89最大.故答案选:C.