You are the administrator for a company’s SharePoint Online environment. The environment hosts several site
collections that are used to store and collaborate on Documents that contain sensitive customer information.
A user in the customer relationship department must share a document that contains scheduling and project
information with an external vendor. Only the external vendor and department user must access the
document.
You need to ensure that the external vendor can access and collaborate on the document without exposing
sensitive customer information.
Which two actions can you perform? Each correct answer presents a complete solution.

A.
Create a document library for the document and require sign-in.

B.
Share the site containing the collaboration document and require sign-in.

C.
Share the document and require sign-in.

D.
Share the document and do not require sign-in.

Explanation:
External users sign in to the service by using a Microsoft account or a work or school account.
We can share the document through a new document library or share the document directly.
Incorrect answers:
Not B: We should not share the entire site. We should just share the document.
Not D: External users must sign in to the service by using a Microsoft account or a work or school account. https://support.office.com/en-ca/article/Manage-sharing-with-external-users-in-Office-365-SmallBusiness-2951a85f-c970-4375-aa4f-6b0d7035fe35?ui=en-US&rs=en-CA&ad=CA