Since these questions apparently are from a PADI course workbook, I suspect that if you had the workbook, the material presented before the questions would tell you what the correct answer should be. Since many of us do not have the workbook, we are trying to match our working knowledge base gained from whatever PADI course(s) we have taken, or SB threads/posts, against the workbook answer without having read the PADI course material. Personally, I don't care if I choose the wrong answer because ultimately I have learned something.