In both sets below, the same two letters, in the same, consecutive order, will change the letter strings into complete words. The two letters may be added or inserted anywhere in the words. (The two letters are different for each set.

Set I 

TSCH

AMBO

SLLET 

SFF

Set II

FER

DEC

DEPL

BUANT 

Answers:

 

Set I: The missing letter are KI:

KITSCH

AKIMBO

SKILLET

SKIFF

 

Set II: The missing letters are OY:

FOYER

DECOY

DEPLOY

BUOYANT