You need to ensure that you can manage Server2 from Server1 by using Server Manager on Server1

You have two servers named Server1 and Server2 that run Windows Server 2012 R2. Server1 and
Server2 are part of a workgroup.
On Server1, you add Server2 to Server Manager.
When you attempt to connect to Server2 from Server Manager, you receive the following error
message: “Credentials not valid.”
You need to ensure that you can manage Server2 from Server1 by using Server Manager on Server1.
What should you do?

A.
On Server 2, run the Configure-SmRemoting cmdlet.

B.
On Server 1, run the Set-NetFirewallRule cmdlet.

C.
On Server 1, run the Set-Item cmdlet.

D.
On Server 2, install the Remote Server Administration Tools (RSAT).

Explanation:
Since they are both workgroup members, server 2 will have to be added to server 1 as a trusted host