Which sentence correctly uses a comma to separate an introductory subordinate clause? visitors marvelled at the beauty created by fifty american painters and sculptors, when the great hall opened in 1897. when the great hall opened in 1897, visitors marvelled at the beauty created by fifty american painters and sculptors. opened in 1897, visitors marvelled at the beauty created by fifty american painters and sculptors in the great hall. in the great hall, visitors marvelled at the beauty created by fifty american painters and sculptors in 1897.