Answer:
\, /, -
Explanation:
The three symbols are forward slash, backward slash, and the hyphen. These were allowed in previous versions of the MS Word. However, since the MS Word 2016 and a little earlier, these three symbols have been banned. And you will immediately get a message if you use these, to correct, and only then the file will be saved with that new name, and that must not have the forward or backward slash or the hyphen.
