Yes, you can do it. But you have to think outside the box. (Pun intended). The checkboxes are not an actual option on Sporcle. Sproutcm has inserted them himself. So I think in the hint column you would put whatever the topic is--say "Sports"--and then put <br> after it so that there is a line break, and then put the little box symbols, which you can copy from somewhere online. Or right here. You'd do it multiple times; however many different answers there are. And each time you would replace one empty box with one x box.
Hint column
Sports<br>☒□□□
Sports<br>☒☒□□
Sports<br>☒☒☒□
And so forth.
And in the answer column you would put all of the answers for each subject; the order doesn't matter as long as each one gets a turn to be the first one listed so it shows up as an answer square.
Sports<br>☒□□□ Basketball/baseball/football/golf
Sports<br>☒☒□□ Golf/baseball/golf/football
Sports<br>☒☒☒□ Football/golf/baseball/football
And so forth.
All of the answers have to be accepted for that topic every time so that it doesn't matter what "stage" the user is at in that subject for it to be registered as correct.
When you move on to a new subject, replace the the subject heading and the set of answers.
At least I think that's what he did. I'm kind of rusty on this level of clever quiz making. Anyone is free to correct me if I'm getting it wrong.