Eight students A, B, C, D, E, F, G and H sit around a circular table, equidistant from each other, facing the centre of the table, not necessarily in the same order. B and D sit neither adjacent to C nor opposite to C. A sits in between E and D. F sits in between B and H. Which one of the following is definitely correct?

Theme: Circular seating arrangement / logical reasoning.

Fix C anywhere. Since B and D are neither adjacent to C nor opposite to C, the only possible seats for B and D are the two positions at distance 3 from C; hence B and D are opposite each other.
A sits in between E and D ⇒ A is adjacent to both E and D. F sits in between B and H ⇒ F is adjacent to both B and H. This gives two mirror-image valid arrangements.

(a) B sits in between A and G — In one valid arrangement, B is between A and G; in the mirror arrangement, B is between G and H. Not definite.
(b) C sits opposite to G — In the valid arrangements, G is adjacent to C, not opposite. False.
(c) E sits opposite to F — In one valid arrangement E is opposite F, but in the mirror arrangement E is opposite H. Not definite.
(d) None of the above — Since (a), (b), and (c) are not definitely correct, this is correct.