in the series,
first writing the first letters alone
P
O
N
M
here we can see that this is the descending order of alphabetic order.So the first letter of thenext term must be the one below M,thault is L.
Now taking 2nd term
M
O
Q
S
here,we can see that these are alternative terms (2nd term after each letter)in ascending order.
so the 2nd letter of next term must be the alternative term after S, that is U
now taking the 3rd terms
T
Q
N
K
here we can see that Q is the 3rd term after T in descending order
Q is the 3rd term after N in descending order after Q and similarly K after N
so the 3rd letter in next term of the series is the 3rd letter in descending order after K
So the 3rd term is H
therefore, the next term in the series is LUH