At a card player's club, the poker players had a contest with the blackjack players to see who could win the most money. the appropriate design for testing the significance of the difference between the means is

Your not allowed to ask their age, only if they're above 18, you cannot ask if they have ever been arrested, convicted, or spent time in jail prior to employment (you can however ask a question like "perhaps this job required security clearance, would you be able to attain it? "). you also cannot ask the severity or nature of any disabilities they have but similar to criminal record can ask if they are able to preform the job safely. in addition to this, you can ask *after* an interview if they're married for insurance reasons. so it appears to be c and d, but if you can only chose one it would probably be b.