Identify `(A)` to `(F)` :

Explanation

`D.U. ` in `(A)((2xx6+2)-10)/(2)=2^(@)`
`D.U.` in `(B)=((2xx6+2)-12)/(2)=1^(@)`
In (C) ,there is no degree of unsaturation because it is an alkane. Also, `(D)` and `(E)` are aldehydes and `(F)` is an acid.
Formul of `(D)implies` `(C_(2)H_(4)O)/((-CHO)/(CH_(3)-))]implies(CH_(3)-CH=0)` (Ehernal or Accetaldehyde)
Formula of `(E)implies` `(C_(2)H_(2)O_(2))/((-CHO)/(CHO))]implies[underset(O)underset(||)CH-underset(O)underset(||)CH]` (Gloyoxal or Ethane`-1,2-`dial)
Formula of `(F)implies (C_(3)H_(6)O_(2))/((-COOH)/(C_(2)H_(5)-))]implies C_(2)H_(5)-COOH`(Propanoic acid)
Total `C` atoms in `(A)=6`
Total `C` atoms in `(D)+(E)=4`
Two `-C-` atom compound is missing.
Glyoxal has bi`-` functional group, therefore, it has to combine with both functional groups. So, there should be `2 mol` of `(D) (CH_(3)CHO)`.

Reactions `:`
or
`[{:(2mol,CH_(3)-CHO,+,OCH,-CHO),( , (D),,(E) ,):}]`