How many people have their interviews between L and M?

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Step-by-step solution:

1. From “only four people between N and Zoology” we get $|pos(N)-pos(Z)|=5$. Since neither is on Sunday ($7$), the only possible position pairs are $(1,6)$ or $(6,1)$.

2. If Zoology were at $1$, then P (immediately after Zoology) would be at $2$, forcing J at $5$ ($2$ people between P and J). Psychology must be before J and not on Wednesday ($3$); but P and N can't be Psychology, leaving only position $4$ for Psychology. Then Statistics would be at $7$ and Economics at $6$, conflicting with N/subject constraints. So Zoology cannot be at $1$.

3. Therefore Zoology is at $6$, P at $7$, and N at $1$. With P at $7$, J must be at $4$ ($2$ between). Psychology is before J and not on $3$, and neither N nor P likes Psychology, so Psychology must be at $2$.

4. Two between Psychology ($2$) and Statistics means Statistics is at $5$, so Economics is immediately before it at $4$ — hence J (at $4$) likes Economics.

5. Number between P ($7$) and Economics ($4$) is $2$, so number between J ($4$) and English must be $2$, giving English at $7$ (since N at $1$ does not like English). Thus P at $7$ likes English.

6. One person between English ($7$) and K gives K at $5$, so K likes Statistics. Remaining subjects are Sociology and Mathematics for positions $1$ and $3$.

7. Sociology is immediately after O, so Sociology must be at $3$ and O at $2$ (O is Psychology). Therefore N at $1$ must like Mathematics.

8. The remaining two persons (L and M) occupy positions $3$ and $6$. Since L is after M, M is at $3$ and L at $6$.

Final arrangement (pos: person - subject):
1: N - Mathematics
2: O - Psychology
3: M - Sociology
4: J - Economics
5: K - Statistics
6: L - Zoology
7: P - English

Thus L is at position $6$ and M at position $3$, so the number of people between them is $6-3-1=2$.

FINAL_ANSWER: a

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