Explanation:

- Option 1: No improvement

- The original segment "watching the procession" is grammatically correct and clearly conveys that each person involved was an active participant in observing the procession.

- Each person who was physically there and saw the event in real-time was given a flag.

- Correct and clear as is.

- Option 2: watched the procession

- This implies that the action of watching has already been completed, which does not match the context of ongoing participation.

- Option 3: having watched the procession was provided

- This is mixed tense and suggests actions completed in the past, which could be confusing in terms of timing.

- Option 4: to watching the procession

- This is grammatically incorrect. The usage of "to" here is incorrect for linking the parts of the sentence.