A company deploys an Office 365 tenant. You assign the roles to users as shown in the following
table:

User3 must be able to monitor the health of the Exchange Online service. You must use the principle
of least privilege to assign permissions to User3.
You need to assign permissions to User3.
Which three actions should you perform? Each correct answer presents part of the solution.

A.
Assign User3 the service administrator role in Office 365.

B.
Sign in to the Office 365 portal as User1.

C.
Sign in to the Office 365 portal as User2.

D.
Grant User3 administrative permissions in Exchange Online.

E.
Assign User3 the global administrator role in Office 365.

Explanation:
Only the global administrator can delegate service administrator role.

http://onlinehelp.microsoft.com/en-in/office365-enterprises/ff637584.asp