assertion reason

assertion seems false , since oxo is used for ketonic grps , and dis is an aldehyde grp , for aldehydes we use formyl/ aldo when it is a substituent.

however reason is true . the order of priority of functional grps for naming poly functional grps is :

1] Carbocations
2] Carboxylic acid
3] Acid anhydride
4] Esters
5] Acyl halides
6] Amides
7] Nitriles
8] aldehydes
9] Ketones
10] Alcohols
11] Thiols
12] Amines
13] Ether
14] Sulphides
15] Alkenes
16] Alkynes
17]alkanes
18] Alkyl halides
19] Nitro grp