The best reagent to carry out the following conversion is:
$3$-hydroxyethylcyclopentane-$1$-carbaldehyde $\rightarrow$ $1$-ethyl-$3$-methylcyclopentane (with a hydroxy group on the ethyl side chain).
(Note: The image shows the reduction of an aldehyde group $-CHO$ to a methyl group $-CH_3$ while keeping the secondary alcohol $-CH(OH)CH_3$ intact.)

• A
  $Red \ P / I_2$
• B
  $LiAlH_4, Et_2O$
• C
  $Zn-Hg / HCl$
• D
  $(i) N_2H_4; (ii) \mathop O\limits^\Theta H, \Delta$