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.

Who attends immediately before A?

The correct option is D.

Step-by-Step Logic and Ordering:

Let us arrange the 7 persons attending the event in sequential order from position 1 to position 7.

1. Analyze the clue regarding G and C:
"G attends the event three persons after C."
This means if C is at position $x$, then G is at position $x+3$ (i.e., C, _, _, G).

2. Analyze the clue regarding B and C:
"B attends the event immediately before C."
So, the order is B, C, _, _, G.

3. Analyze the clue regarding B and E:
"Only one person attends the event between B and E."
Since C immediately follows B, E cannot be placed after B. Therefore, E must be placed 2 positions before B.
So, the sequence becomes: E, _, B, C, _, _, G.

4. Determine the exact positions of these persons:
The block "E, _, B, C, _, _, G" contains 7 positions in total.
Thus, the 7 positions (1 through 7) are filled as follows:
Position 1: E
Position 2: _
Position 3: B
Position 4: C
Position 5: _
Position 6: _
Position 7: G

5. Analyze the clue regarding D, E, and A:
"D attends the event four persons after E but before A."
Since E is at position 1, D must be at position $1+4=5$.
Since D is before A, and the remaining available positions are 2 and 6, A must be at position 6.

6. Analyze the remaining positions and persons:
"Three persons attend event between A and F."
Since A is at position 6, three persons between them means F is at position $6-4=2$.
This perfectly fills all positions!

Final Arrangement (Positions 1 to 7):
1: E
2: F
3: B
4: C
5: D
6: A
7: G

Conclusion:
The person attending immediately before A (position 6) is D (position 5).