The correct option is D Both 1 and 2
a) This is Stephen's reaction, which involves the conversion of an alkyl cyanide to an aldehyde using SnCl2/HCl as a reducing agent.
b) DIBAL−H, also reduces the nitrile group to an aldehyde.
c) Pd−BaSO4 will not reduce alkyl cyanide into aldehyde.
R−C≡NSnCl2/HCl−−−−−−−→R−CHO
R−C≡NDIBAL−H, H+/H2O−−−−−−−−−−−−−−→R−CHO