Directions: Read the following instructions carefully and answer the related question:

A certain number of individuals are sitting in a straight row facing north.

Person A sits at the extreme left end of the row. Two persons sit between A and B. C sits third to the right of B. D sits third to the right of C. E sits third to the right of D. Exactly one person sits between E and F. F sits at the extreme right end of the row.

Who among the following sits third to the left of D?

The correct answer is C.

Let us determine the arrangement of individuals sitting in a row facing north step-by-step from left to right:

1. Position of A: Person A sits at the extreme left end of the row (Position 1).
2. Position of B: Two persons sit between A and B, placing B at Position 4.
3. Position of C: C sits third to the right of B (Position 4 + 3), placing C at Position 7.
4. Position of D: D sits third to the right of C (Position 7 + 3), placing D at Position 10.
5. Position of E: E sits third to the right of D (Position 10 + 3), placing E at Position 13.
6. Position of F: Exactly one person sits between E and F, with F at the extreme right end, placing F at Position 15.

The complete seating arrangement from left to right is:
Position 1: A
Position 2: _
Position 3: _
Position 4: B
Position 5: _
Position 6: _
Position 7: C
Position 8: _
Position 9: _
Position 10: D
Position 11: _
Position 12: _
Position 13: E
Position 14: _
Position 15: F

To find who sits third to the left of D (who is at Position 10):
- 1st to the left of D: Position 9
- 2nd to the left of D: Position 8
- 3rd to the left of D: Position 7, which is occupied by C.

Therefore, C sits third to the left of D.