Hi,<br/><br/>Is it ok to use two prepositions like this (in this case, 'on' and 'by') without comma? Example: it was an attack on the cops by the cops.<br/><br/>2) Again, which preposition is right here? They fastened him 'on' the stretcher. They fastened him 'to' the stretcher. Is it 'on' or 'to'?<br/><br/>Regards,