In the following reaction,  $\text{HC}\equiv \text{CH}\stackrel{\text{A}}{\to }{\text{CH}}_{\text{3}}\text{CHO}$,

‘A’ can be? 

• A

  ${\text{20 \% H}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{+ HgSO}}_{\text{4}}$

• B

  B₂H₆ then treatment with H₂O₂/^-OH

• C

  Both 1 and 2

• D

  Cl₂ in water