Aldol condensation does not occur between
Two different aldehydes
Two different ketones
An aldehyde and a ketone
An aldehyde and an ester
An aldehyde and an ester
The explanation for the correct option:
Option (D): An aldehyde and an ester
The explanation for the incorrect options:
Option (A): Two different aldehydes
Option (B): Two different ketones
Option (C): An aldehyde and a ketone
Therefore, aldol condensation does not occur between an aldehyde and an ester, option (D) is the correct option.