Directions: Read the following information carefully and answer the questions given below.

Six persons A, B, C, D, E and F sit around a circular table facing towards the centre, with equal distance between adjacent persons. Each of them is of a different age. The sum of the ages of the persons sitting opposite to each other is 40 years. None of them is less than 15 years old and greater than 25 years old.

E's age is 24 years. F sits opposite to the person who is 21 years old. B, who is the youngest person, sits immediately to the left of D. A sits second to the right of F. D is 4 years older than A.

Which of the following individuals is seated immediately to the right of the oldest person?

The correct answer is A.

Step 1: Understanding the Age Constraints and Opposite Pairs
Six persons (A, B, C, D, E, and F) sit around a circular table facing the centre.
Key facts given regarding their ages:
1. None of them is less than 15 years old and greater than 25 years old.
2. The sum of the ages of persons sitting opposite to each other is 40 years.
3. E's age is 24 years. Therefore, the age of the person sitting opposite E must be:

$40-24=16$

4. F sits opposite the person who is 21 years old. Therefore, F's age must be:

$40-21=19$

Step 2: Calculating Individual Ages
We know the three opposite age pairs must each sum to 40:
- Pair 1: E (24 years) and Person 1 (16 years)
- Pair 2: F (19 years) and Person 2 (21 years)
- Pair 3: Person 3 and Person 4 (ages sum to 40)

We are given that B is the youngest person and D is 4 years older than A:

$D=A+4$

If B is 16 years old (the youngest of all persons), then the remaining ages for A, C, and D must be selected from the set {18, 21, 22} such that:

$18+4=22$

Thus, we get:
- B = 16 years old (Youngest, opposite E)
- A = 18 years old (opposite D)
- F = 19 years old (opposite C)
- C = 21 years old
- D = 22 years old
- E = 24 years old (Oldest)

Step 3: Determining the Seating Arrangement
Since everyone faces the centre of the circle:
- Moving Clockwise corresponds to moving to the Left of a person.
- Moving Counter-Clockwise corresponds to moving to the Right of a person.

Let us number 6 positions clockwise around the table as Position 1 through Position 6:
1. Place F (19 yrs) at Position 1.
2. The person opposite F (21 yrs, which is C) sits at Position 4.
3. A (18 yrs) sits second to the right of F (2 steps counter-clockwise from Position 1), placing A at Position 5.
4. The person opposite A is D (22 yrs), so D sits at Position 2.
5. B (16 yrs) sits immediately to the left of D (1 step clockwise from Position 2), placing B at Position 3.
6. The remaining position, Position 6 (opposite B), is occupied by E (24 yrs).

Step 4: Answering the Question
The oldest person is E (24 years old), who is seated at Position 6.
Moving immediately to the right of E (1 step counter-clockwise from Position 6) leads to Position 5.
Position 5 is occupied by A.
Therefore, A is seated immediately to the right of the oldest person.