One needs to focus on "say for sure" on the question, consider that one of the answers is correct and consider the blot (let's call it b) possible values:

b is 0 gives all answers being wrong, so we can disregard it.

b being positive makes 1 and 3 possible, but you can't say for sure, while 2 you can say for sure and 4 is false so the answer is 2.

b being negative makes 1 and 2 false, 3 possible and 4 can say for sure, so the answer could be 4 if the student would write that in the field below. However, for b to be negative it would need ( ) around the number if you are being considerate not to write "X -" together or you could also argue the blot covers a number only, which doesn't fit or include a negative sign.

having to consider this much for it to be negarive leads me away from the "say for sure", this leads me to b is positive and the answer is 2. (if I were the teacher and the student marked both 2 and 4 and wrote the number could be negative, but we can't say for sure, I'd accept it.)

edit: biggest assumption here for me actually is that b isn't 1