You need to ensure that external users can access and edit the documents without affecting the security of other content

You are the Office 365 administrator for your company. The company uses Office 365 ProPlus and
has multiple Microsoft SharePoint Online sites.
The company recently started a project that requires employees to collaborate with external users
on the development of a set of documents that are stored in a team site.
You need to ensure that external users can access and edit the documents without affecting the
security of other content.
What should you do?

A.
Configure and share guest links to the documents for the external users.

B.
Configure and share a guest link to the existing SharePoint team site for the external users.

C.
Share documents by using the Share function and adding the external users to the Contributors
group.

D.
Share the existing SharePoint team site by using the Share function and adding the external users
to the Contributors group.

Explanation:
If you perform work that involves sharing documents or collaborating directly with vendors, clients,
or customers, then you might want to use your sites to share content with people outside your
organization who do not have licenses for your Office 365 subscription.
There are three ways that you can do this:
* You can send users a guest link that they can use to view individual documents on your site
anonymously.
* You can share an entire site by inviting external users to sign in to your site using a Microsoft
account* or a work account.
* You can share individual documents by inviting external users to sign in to your site using a
Microsoft account* or a workacct_short.

Share sites or documents with people outside your organization
https://support.office.com/en-AU/article/Share-sites-or-documents-with-people-outside-yourorganization-5f4cee39-5c91-4dc8-8fb1-96bca76f4eb0