L, M, N and O are to be seated in a row from left to right. However, N and O cannot be together. Moreover, M cannot be in the third place from the left. L and M are sitting beside each other. Considering the seating from left to right, which of the following must be true?

Let the four positions from left to right be represented as 1, 2, 3, and 4.
Constraints:

N and O cannot be adjacent (NO or ON is not allowed).

M

=3.

L and M must be together (LM or ML).

Let's test the possible positions for the pair LM or ML:

Case 1: M and L occupy positions 1 and 2.

If M=1,L=2: The remaining positions are 3 and 4 for N and O. This forces N and O to be adjacent in positions 3 and 4, which violates Constraint 1.

If L=1,M=2: Similarly, 3 and 4 must be filled by N and O, violating Constraint 1.

Case 2: M and L occupy positions 2 and 3.

Since M

=3, we must have L=3 and M=2.

Now positions 1 and 4 are left for N and O. Since they are separated by M and L, they are not together, which satisfies Constraint 1.

The arrangements could be: N,M,L,O or O,M,L,N.

In both valid arrangements, L is at the third place.

Case 3: M and L occupy positions 3 and 4.

Since M

=3, we must have M=4 and L=3.

Positions 1 and 2 are left for N and O. This forces them to be together, violating Constraint 1.

Therefore, L must be at the third place from the left.