The old woman had a letter from her son in the army ___ to her.
There was an old man wandering about the corner _____ waiting for someone.
John couldn’t finish his words ______ something had struck his throat.
______was known to all,William had broken his promise ______ he would give us a rise.
Students shouldn’t be given so difficult a problem ______they can not work out.
____ is clear to us all, students should obey the school’s rules.