Some people with black belts , or black and red belts , are performing martial arts on a green mat .
It is likely that several people , who met at judo class , watched the game together .
It is impossible that several people , who met at judo class , watched the game together .
It is likely that several people , who met at judo class , watched the game together .
Several people , who met at judo class , watched the game together .