Which of the following is Clemmensen reduction?

• A
  $RCOCl \xrightarrow{H_2, Pd-BaSO_4} RCHO + HCl$
• B
  $RCN \xrightarrow{SnCl_2, HCl, H_3O^+} RCHO + NH_4Cl$
• C
  $RCHO \xrightarrow{Zn-Hg, \text{Conc. } HCl, \Delta} RCH_3 + H_2O$
• D
  $RCOR \xrightarrow{i) H_2N-NH_2, ii) KOH, HO-CH_2-CH_2-OH} R-CH_2-R$