The correct option is 23yr.

Step-by-step Explanation:

Let's analyze the given conditions step-by-step to determine the position and experience of each person sitting in a row facing north.

1. Identify the given experiences and vowels:

The experiences given are: 15yr, 7yr, 2yr, 23yr, 19yr, 6yr, 12yr.

The even number experiences are: 2yr, 6yr, and 12yr.

The persons with vowel names are E, A, and U.

According to the problem, persons with vowel names must have an even number of years of experience (2yr, 6yr, or 12yr), and none of them sit at the extreme ends or in the exact middle (position 4) of the 7-person row.

Thus, E, A, and U can only occupy positions 2, 3, 5, or 6, and their experiences must be among {2yr, 6yr, 12yr}.

2. Determine the experience of A:

The problem mentions a person having experience "2.5 times of A".

Since experiences are integers (15, 7, 2, 23, 19, 6, 12), let's check which experience when multiplied by 2.5 gives another available experience:

$6\times 2.5=15$

Therefore, A must have 6yr of experience, and the person with 2.5 times A's experience has 15yr of experience.

3. Analyze the seating arrangement positions:

Let the 7 positions in the row from left to right be numbered 1, 2, 3, 4, 5, 6, 7.

Vowel persons (E, A, U) must sit in positions {2, 3, 5, 6}.

Since A is a vowel, A is at position 2, 3, 5, or 6.

The number of persons to the right of A equals the number of persons to the left of the one with 15yr experience.

If A is at pos 2, persons to right of A = 5. So, 15yr person has 5 persons to their left, placing 15yr person at pos 6.

If A is at pos 3, persons to right of A = 4. So, 15yr person has 4 persons to their left, placing 15yr person at pos 5.

If A is at pos 5, persons to right of A = 2. So, 15yr person is at pos 3.

If A is at pos 6, persons to right of A = 1. So, 15yr person is at pos 2.

4. Placing S and the 23yr experience person:

Three persons sit between S and the one with 23yr experience.

One person sits between S and A.

The person with least experience (2yr) sits second to the left of D.

Since U does not have least experience (2yr) and A has 6yr, the person with 2yr experience must be E (the remaining vowel person).

Thus, E has 2yr experience, A has 6yr, and U has 12yr.

Since E (2yr) is second to the left of D (pos of D = pos of E + 2), E must be at pos 2 or 3, so D is at pos 4 or 5.

5. Evaluating positions systematically:

Since E (2yr) sits second to left of D, E can be at pos 2 (D at pos 4) or E at pos 3 (D at pos 5).

Case: E is at pos 2 (2yr) and D is at pos 4.

Then A can be at pos 6. Since 1 person is between S and A, S is at pos 4, which conflicts with D being at pos 4.

Or if A is at pos 3, then 1 person between S and A places S at pos 1 or pos 5.

If S is at pos 1, 3 persons between S and 23yr means 23yr is at pos 5.

Then A is at pos 3 (6yr). Number of persons right of A = 4, so 15yr is at pos 5. But 23yr is at pos 5, contradiction.

If S is at pos 5, 3 persons between S and 23yr means 23yr is at pos 1.

With S at pos 5 and A at pos 3 (6yr), right of A = 4, so 15yr is at pos 5 (S = 15yr).

Now vowel positions {2, 3, 5, 6}: E is at pos 2 (2yr), A is at pos 3 (6yr), S is at pos 5 (15yr - not a vowel, valid), so U (vowel, 12yr) must be at pos 6.

Positions filled so far:

1: (23yr)

2: E (2yr)

3: A (6yr)

4: D

5: S (15yr)

6: U (12yr)

7: remaining person

The remaining positions are 1, 4, 7 for persons V and B, and D is at pos 4.

B cannot sit adjacent to S (pos 5), so B cannot be at pos 4 or 6. Thus B must be at pos 1 or pos 7.

The neighbors of B have more experience than B. Also, B does not have the highest experience (23yr), so B cannot be at pos 1 (which has 23yr).

Hence, B is at pos 7, and V is at pos 1!

6. Conclusion:

Position 1 is occupied by V, who has an experience of 23yr.