That's not how csvs work though. Everyone knows you sometimes use dots as decimals but as separators in column 3 and 17, but not in rows that rhyme with their first entry except on tuesdays.

Or they are overly literal and second guessed their initial reading of it. Something I could definitely see an autistic or ADHD kid doing.

I've had teachers who draw X's fast enough they just do it in one motion and it looks as above.

Looks like an alpha, so I assume this is all correct.

It's an "X" to indicate incorrect answer. The teacher has 100+ papers to grade and a lesson plan to get together for tomorrow and doesn't have time to make their marks look pretty.

I used to have a teacher (and multiple others since then) back in the 90s who also used the same squiggly to indicate correct answers. Not sure what the origin is, but I've also used it since

It's an alpha and short for: αλλ ριγητ

In addition to what others have said (this is an X), American teachers traditionally use red pen to mark incorrect answers/correct mistakes.

The teacher marked these as incorrect.

i.
ii.
iii.