A student wants to synthesize propionitrile from ethanol CH₃CH₂OH → ?CH₃CH₂CN. Which of these reagents would work? (Select all that apply.)
a) KCN (Potassium cyanide)
b) H₂SO₄ (Sulfuric acid)
c) NaCN (Sodium cyanide)
d) PBr₃ (Phosphorus tribromide)