Explanation:

Let's analyze the statements:

- A is lighter than only one person: So, A is the 2nd heaviest.

- C is heavier than F but lighter than D: D > C > F.

- E is heavier than D: So, E > D.

- F is not the lightest: At least one is lighter than F.

- The 3rd lightest weighs 67 kg.

Let’s order by weight:

- E > D > C > F (from above clues), and A is 2nd heaviest.

- The heaviest: One person is heavier than A. This must be E.

- So, order: E > A > D > C > F. B is missing.

- F is not the lightest, so B must be the lightest.

So, the ordering: E > A > D > C > F > B

Given the 3rd lightest is 67 kg

So, positions:

1. E

2. A

3. D

4. C

5. F

6. B

3rd lightest: Counting from lightest, so B (lightest), F, C (third lightest) — but from most to least, third is D; from least to most, third is C.

But if B is lightest, F is above B, C is above F, so 3rd lightest is C, who is 67 kg.

So, weights order (lightest to heaviest):

B < F < C(67) < D < A < E

From options, what is the weight of B?

- It's less than 67, only option possible is 57 kg.

So:

?? Option 3: 57 is correct.

- B is 57 kg, F is more than 57 but less than 67, C is 67, others are heavier.

Option 3: 57 kg is the answer.