Solution Breakdown

Let's determine the seating arrangement by combining the clues in a logical order.

Step 1: Understand the Orientation

There are 7 people in a single line facing East. This is a key detail, as it means their right side points South and their left side points North. We can visualize the 7 seats from North to South.

(North End) --- 1 --- 2 --- 3 --- 4 --- 5 --- 6 --- 7 --- (South End)

Step 2: Apply the Clues

• Clue: "D is sitting third from the south end."
  The south end is position 7. Counting three places in from there puts D in position 5.
  _   _   _   _   D   _   _
• Clue: "C is immediate to the right of D."
  Since they face East, D's right is to the South. This places C in position 6.
  _   _   _   _   D   C   _
• Clue: "B is at one of the extreme ends and has E as his neighbour."
  This means the pair B-E must be at an end. They cannot be at the South end because position 6 is already occupied by C. Therefore, B must be at the North end (position 1) and E must be his neighbour (position 2).
  B   E   _   _   D   C   _
• Clue: "G is between E and F."
  This creates the block E-G-F. Since we know E is in position 2, G must be in position 3 and F in position 4.
  B   E   G   F   D   C   _

Step 3: Determine the Final Arrangement

The only person not yet placed is A, and the only empty seat is position 7 at the South end.

The final arrangement from North to South is: B, E, G, F, D, C, A.

Conclusion

The question asks for the persons at the extreme ends. Based on our arrangement:

• The person at the North end is B.
• The person at the South end is A.

Therefore, the correct answer is A and B, which corresponds to option B.