`A underset("dil" H_(2)SO_(4))overset(K_(2)Cr_(2)O_(7))to B underset(H_(2)O)overset(CH_(3)MgI)to CH_(3)-underset(OH)underset(|)overset(CH_(3))overset(|)C-CH_(3)`. The reactant A is
A. `CH_(3)CHOHCH_(3)`
B. `CH_(3)COCH_(3)`
C. `C_(2)H_(5)OH`
D. `CH_(3)COOH`