Statement-I : Aldehydes and ketones undergo nucleophilic substitution reactions.Statement-II : H- and R- are strong bases.

R−CO||−H  .   .   .  AldehydeR−CO||−R  .   .   .  ketoneR−CO||−H   (or)  R−CO||−R→Nu−R−CO||−Nu is not possible because H- and R- are very strong bases difficult to replace.H- is a conjugate base a very acid H2 and R- is a conjugate base R-H