Assertion (A) : Acetone is a functional group isomer of propionaldehyde.Reason (R) : Aldehydes and ketones are functional group isomers.Both (A) and (R) are correct and (R) is the correct explanation of ABoth (A) and (R) are correct but (R) is not correct explanation of A(A) is correct but (R) is not correct(A) is incorrect but (R) is correct

Let's analyze each statement:

Assertion (A): Acetone is a functional group isomer of propionaldehyde. This statement is correct. Acetone (CH3COCH3) and propionaldehyde (CH3CH2CHO) both have the same molecular formula (C3H6O), but different functional groups (a ketone in acetone and an aldehyde in propionaldehyde), making them functional group isomers.

Reason (R): Aldehydes and ketones are functional group isomers. This statement is also correct. Aldehydes and ketones can indeed be functional group isomers of each other, as they can have the same molecular formula but different functional groups.

So, both the Assertion and Reason are correct, and the Reason is a correct explanation of the Assertion. Therefore, the correct answer is "Both (A) and (R) are correct and (R) is the correct explanation of A".