Could a ct scan tell if a meningioma is benign?

No, but most of them: Only a pathology review can tell if there are any signs of atypia in a meningioma. Most of them are perfectly benign; only rare meningioma show signs of possible cancer and or risk of recurrence. This can not be determined by means of ct scan which simply gives you an image of the tumor.

No: Most meningiomas are benign. The only way to know for sure is with pathologic review after resection.

No: Truly the answer is no as the only way to confirm that one is bengin is by biopsy. It is not uncommon, for instance in the eldely where the risk of surgery may be much greater, when a brain tumor has features highly consistent with meningioma for the work up to stop after the ct or mri. If this were a board exam i believe the best answer, however, would be no.