Bulla suspected that ki attacks might be able to hit ghosts, but she didn't want to risk blasting holes through people's walls to test that theory.

"Kind of. But also we could try getting them a pen and paper. If they can pick things up to throw them, they should be capable of picking up the pen and drawing on the paper. Or we could write 'yes' and 'no' on the paper and get them something to point with instead while we ask questions."

It was entirely possible that the ghosts would just throw things at them instead. There was no guarantee this would work. It was something to try, nothing more.