21. Find the missing letters in the following series.
AK, EO, IS, __________, QA, UE
22. Find the missing letters in the following series.
ELFT, GLHT, ILJT, __________, MLNT
24. Find the missing letters and numbers in the following
series.
C2A, E5D, G8G, I11J, __________
25. Find the missing letters in the following series.
QAR, RAS, SAT, TAU, __________