Solutions
Given: K, L, M, N, O, P, S are seven friends siting in a row facing north.
The one who sits fourth to the left of S, sits at one of the extreme ends of the row.
N is an immediate neighbour of both P and S.
Case I:

K sits fourth to the right of M (This statement cancels the possibility of Case I, so considering Case II).
L sits to the immediate right of K.
And, O sits at the remaining place (Extreme left end).
Case II:

Here, N sits fourth from the right end of the row.
Hence, the correct answer is 'Option 2'.