3- All instructors who usually come to class on time are good teachers, Mr Sami Comes to his classes on time. He must be a good teacher. Valid Invalid 4- If the match is burning then there is oxygen in the room. The match is not burning. Therefore, there is no oxygen in the room. Valid Invalid 5- Every time there is someone in the garden, our neighbor's dog barks. Now its barking, so someone must be in the garden. Valid Invalid