Use of comma

[Allifathima]

1a. John sat on a park bench, eating his lunch.
1b. John sat on a park bench eating his lunch.
2a. John sat on a bench with David, eating his lunch next to him.
2b. John sat on a bench with David eating his lunch next to him.
Please correct the above.
Thanks.

[Beeesneees]

1a. John sat on a park bench, eating his lunch.
1b. John sat on a park bench eating his lunch. < the bench was not eating lunch
2a. John sat on a bench with David, eating his lunch. <John is eating lunch.
2b. John sat on a bench, with David eating his lunch next to him. < David is eating lunch.
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