Seven people, A, L, M, I, R, H and S, are sitting in a row, facing north.
Only A sits to the left of S. Only four people sit between A and H. Only I sits between L and R and L is not an immediate neighbor of H.

Who sits at the extreme right of the line?

The correct option is M.

Let's find the arrangement of the seven people (A, L, M, I, R, H, and S) sitting in a row facing north step-by-step:
We have 7 positions from left to right: _ _ _ _ _ _ _

1. "Only A sits to the left of S."
This means S has exactly one person to his left, who is A. Therefore, A must be in the 1st position (extreme left) and S must be in the 2nd position.
Arrangement: A, S, _, _, _, _, _

2. "Only four people sit between A and H."
Since A is in the 1st position, counting 4 positions between A and H (positions 2, 3, 4, and 5), H must sit in the 6th position.
Arrangement: A, S, _, _, _, H, _

3. "Only I sits between L and R and L is not an immediate neighbor of H."
The group of L, I, and R must sit together in 3 consecutive seats: either as (L, I, R) or (R, I, L).
Looking at our remaining empty positions (3rd, 4th, and 7th), the only way to fit 3 consecutive people is in positions 3, 4, and 5.
Since L cannot be an immediate neighbor of H (who is in the 6th position), L cannot be in the 5th position. Thus, L must be in the 3rd position, I in the 4th position, and R in the 5th position.
Arrangement: A, S, L, I, R, H, _

4. Remaining Person:
The only person left to place is M. The only remaining empty seat is the 7th position (extreme right).
Final Arrangement: A, S, L, I, R, H, M

Therefore, M sits at the extreme right of the line.