Seven persons — A, B, C, D, E, F and G — are attending an event one after another, but not necessarily in the same order.
G attends the event three persons after C. B attends the event immediately before C. Only one person attends the event between B and E. D attends the event four persons after E but before A. Three persons attend event between A and F.

How many persons attend between B and A?

The correct option is Two.

Let us step-by-step determine the order of the seven persons (A, B, C, D, E, F, and G) attending the event, numbered 1 to 7 from first to last.

Step 1: Analyze the statements about G, C, B, and E.
1. "G attends the event three persons after C."
This means if C is at position x, G is at position x + 3.
So, the structure looks like: C _ _ G.

2. "B attends the event immediately before C."
So, B is at position x - 1.
The structure expands to: B C _ _ G.

3. "Only one person attends the event between B and E."
This gives two possibilities for E:
- Case 1: E is two positions before B, so the sequence is E _ B C _ _ G.
- Case 2: E is two positions after B (which is between C and G), so the sequence is B C E _ G.

Step 2: Evaluate Case 1.
In Case 1: Sequence is E _ B C _ _ G.
Counting the positions: E (1st), _ (2nd), B (3rd), C (4th), _ (5th), _ (6th), G (7th).
This accounts for all 7 positions!

Now consider: "D attends the event four persons after E but before A."
Four persons after E means D is at position 1 + 4 = 5th position.
So, the sequence becomes:
1: E
2: _
3: B
4: C
5: D
6: _
7: G

Since D must attend before A, A must be placed at position 6.
The sequence is now:
1: E
2: _
3: B
4: C
5: D
6: A
7: G

The remaining empty position (2nd) must be occupied by F:
1: E
2: F
3: B
4: C
5: D
6: A
7: G

Step 3: Check all conditions against this sequence.
- G attends 3 persons after C? C is 4th, G is 7th (4 + 3 = 7). (Satisfied)
- B attends immediately before C? B is 3rd, C is 4th. (Satisfied)
- One person between B and E? B is 3rd, E is 1st (F is between them). (Satisfied)
- D attends four persons after E but before A? E is 1st, D is 5th (1 + 4 = 5), and D (5th) is before A (6th). (Satisfied)
- Three persons attend between A and F? F is 2nd, A is 6th. The persons between them are 3rd, 4th, and 5th (B, C, D — exactly 3 persons). (Satisfied)

Thus, the final arrangement from 1 to 7 is:
E, F, B, C, D, A, G

Step 4: Answer the question.
We need to find how many persons attend between B (3rd position) and A (6th position).
The persons between B and A are C and D, which is a total of 2 persons.