How is Word for the web limited$?$

a$.$ A document opened in Word for the web cannot be simultaneously edited by more than one person.

b$.$ A document opened in Word for the web is formatted as a PDF file, with limited Word editing possible.

c$.$ Word for the web is not as full featured as its desktop equivalent, with fewer ribbon tabs and less functionality.

d$.$ Word for the web can only open Word documents that are less than $15KB$ in size.