What device can Alex use to email his graduation certificate that he only has in physical form?

Using a scanner is the correct choice for emailing a graduation certificate that is only in physical form. A scanner converts the physical document into a digital format, such as a PDF or image file, which can then be attached to an email and sent to the recipient. This process allows for accurate preservation of the document's layout and details, making it easy for others to view and print if necessary.

While a printer is essential for producing hard copies, it does not help in converting physical documents into digital files. A digital camera can take a picture of the certificate, but the image quality may not be as precise or professional as that obtained through scanning. The fax machine, while able to send documents, does not produce a digital file that can be emailed directly; it transmits paper documents over a phone line and is less common in today's digital communication landscape. Thus, a scanner is the most efficient and appropriate tool for this task.