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.

What is the total number of individuals sitting in the row?

The correct answer is 15.

Let us determine the positions of the individuals from left to right in the row facing north:

1. Position of A: Person A sits at the extreme left end of the row. Thus, A is at position 1.

2. Position of B: Two persons sit between A and B. Since A is at position 1, B is positioned at:
$1+3=4$
Thus, B is at position 4.

3. Position of C: C sits third to the right of B. Since B is at position 4, C is positioned at:
$4+3=7$
Thus, C is at position 7.

4. Position of D: D sits third to the right of C. Since C is at position 7, D is positioned at:
$7+3=10$
Thus, D is at position 10.

5. Position of E: E sits third to the right of D. Since D is at position 10, E is positioned at:
$10+3=13$
Thus, E is at position 13.

6. Position of F: Exactly one person sits between E and F, and F sits at the extreme right end of the row. Since F is to the right of E, F is positioned at:
$13+2=15$
Thus, F is at position 15.

Since F is at position 15 and sits at the extreme right end of the row, the total number of individuals sitting in the row is 15.