What does the faculty that is to be the recipient of your exam paper expect, or has stated for the document format? If they explicitly stated Word, and no other format — sending them a .pages document, or .pdf could earn you a failing exam grade depending on their interpretation flexibility of course instructions.
Are most people using Word because the course stated to use Word? You really have no choice in the matter than submit an exported Word document from Pages, if Word was the stated medium.
If you do not export your Pages exam paper to Word, then you are expecting that the receiving faculty has the same version of Pages installed on a Mac, or has access to Pages for iCloud to view your document. I would advise against submitting your exam in other than Word .docx format.