Functional Groups

Step 1: Definition.
A secondary amine has the general formula with two alkyl/aryl groups attached to nitrogen and one hydrogen.
Step 2: Analyze options.
(A) : Correct representation of secondary amine linkage.
(B) : Primary amine group.
(C) : Ammonia, not an amine functional group in an organic chain.
(D) : Protonated ammonium, not the neutral secondary amine group.
Step 3: Conclusion.
Hence, the functional group for a secondary amine is .

Functional Group Identification.
Based on the molecular structure of O₃, the functional group can be identified as a carbonyl group ( ), which is typically found in aldehydes and ketones. This functional group imparts distinctive chemical properties to the compound.