Aldol condensation is a reaction in which an enol or an enolate ion reacts with a carbonyl compound, resulting in the formation of a [REPLACEMENT]-hydroxyaldehyde or a [REPLACEMENT]-hydroxyketone.

Option 1 states that aldol condensation cannot occur between two different aldehydes. This statement is not entirely correct because aldol condensation can occur between two different aldehydes.

Option 2 states that aldol condensation cannot occur between two different ketones. This statement is also not entirely correct because aldol condensation can occur between two different ketones.

Option 3 states that aldol condensation cannot occur between an aldehyde and a ketone. This statement is also incorrect since aldol condensation can occur between an aldehyde and a ketone.

Finally, option 4 states that aldol condensation cannot occur between an aldehyde and an ester. This statement is correct. Aldol condensation typically does not occur between an aldehyde and an ester because the ester functional group is less reactive than the carbonyl group in an aldehyde or a ketone.

Therefore, the correct answer is option 4.