Hey! These questions are like number games, where you are intentionally mislead to look at incomplete data. First line says that 80% of injured set didn’t wear the seatbelt which means if 100 people were injured, 80 didn’t had seatbelts on. Fair enough... But the caveat is what if the survey was conducted among 1000 people and out of the 900 safe people, only 50 wore seatbelt. Now can you confidently say that if you don’t wear a seatbelt, your injury chances would be low? Like the question hasn’t provided any details on the remaining subset. And to confidently prove the conclusion, it would be good to know if atleast 20% of the other group was wearing the seatbelt or not? - so you can generalise your finding
These are like mathematical questions where you are looking to know exact numbers for the sub groups in discussion. And A directly falls in that category.
Problem with D is that, it is a weakener like the example I mentioned above but the question is asking you to find a statement which strengthens your argument.