Step 1: Fix D, G and C using the seat-count clues.
Number the ten chairs 1 to 10 clockwise and place D at chair 1. G is three places to the right of D, so G sits at chair 4. G is also two places to the left of C, which means C sits two places to the right of G, so C sits at chair 6.
Check: is C also five places from D? Chair 1 to chair 6 is a gap of 5, so C sits directly opposite D. That fits, because C and D are both Cricketers and same-sport players always sit opposite each other.
Step 2: Place the Athlete and Swimmer next to each Cricketer.
Cricketers always have an Athlete on their immediate right side and a Swimmer on their immediate left side... more precisely, an Athlete sits immediately before a Cricketer and a Swimmer sits immediately after, reading clockwise (Athlete, then Cricketer, then Swimmer).
For D at chair 1: the Athlete sits at chair 10 and the Swimmer sits at chair 2.
For C at chair 6: the Athlete sits at chair 5 and the Swimmer sits at chair 7.
B and F are the two Athletes, so they occupy chairs 5 and 10 in some order. J and I are the two Swimmers, so they occupy chairs 2 and 7 in some order. Chairs 5 and 10 are five apart, and chairs 2 and 7 are five apart, so both pairs sit opposite each other as required.
Step 3: Use the H clue to pin down I and J exactly.
H sits two places to the right of I. If I were at chair 2, H would fall at chair 4, but chair 4 already belongs to G, so that placement is impossible. So I must sit at chair 7, which puts H at chair 9. That leaves J at chair 2.
Seats fixed so far: chair 1 = D, chair 2 = J, chair 4 = G, chair 6 = C, chair 7 = I, chair 9 = H, and chairs 5 and 10 hold B and F in some order. Chairs 3 and 8 are still open, for the two remaining people A and E.
Step 4: Confirm G is equidistant from I and D.
G is at chair 4. The gap to D (chair 1) is 3 seats, and the gap to I (chair 7) is also 3 seats. This matches the clue that G sits equidistant from I and D, confirming the seating so far is consistent.
Step 5: Work out what G and H play.
Ten seats split into five opposite pairs: (1,6), (2,7), (3,8), (4,9) and (5,10). The pairs (1,6), (2,7) and (5,10) are already used up by Cricket, Swimming and Athletics. That leaves the pairs (3,8) and (4,9) for the remaining two sports, Football and Tennis, one pair each. Chairs 4 and 9 are G and H, so G and H play the same sport, either Football or Tennis.
The Swimmers sit at chairs 2 and 7, so the seats next to them are 1, 3, 6 and 8. Chairs 1 and 6 are Cricketers already, so the people at chairs 3 and 8 (A and E) are the ones sitting next to a Swimmer. Since the Tennis player cannot sit next to a Swimmer, A and E (at chairs 3 and 8) cannot be the Tennis pair, so they must be the Football pair instead.
That leaves G and H, at chairs 4 and 9, as the Tennis pair, and neither of their seats is next to a Swimmer, so this fits the rule cleanly.
Step 6: Final Answer.
G plays Tennis.
\[
\boxed{\text{Tennis}}
\]