Pen or pencil in exams?

[Zafaraaaa]

I used both pen and pencil for my maths exam But usually, as long as the pencil/pen doesn't smudge and become unclear, I dont think they really mind what you use for maths/science subs (the exception here is English though, where you have to use pen)

[Starlight]

What are good erasable pens?

Well they have those pilot frixion ones, but there is another one I can't think of right now, i'll post the name on here later.