You need to ensure that partner accounts are NOT synchronized with Office 365

You are the Office 365 administrator for your company. The company synchronizes the local Active
Directory objects with a central identity management system.
The environment has the following characteristics:
Each department has its own organizational unit (OU).

The company has OU hierarchies for partner user accounts.
All user accounts are maintained by the identity management system.
You need to ensure that partner accounts are NOT synchronized with Office 365.
What should you do?

A.
Configure OU-based filtering by using the Windows Azure Active Directory Sync tool.

B.
In the Windows Azure Active Directory portal, configure OU-based filtering.

C.
Configure user attribute-based filtering by using the Windows Azure Active Directory Sync tool.

D.
In the Windows Azure Active Directory portal, configure user attribute-based filtering.

Explanation:
http://technet.microsoft.com/en-us/library/jj710171.aspx
Company has OU hierarchies for partner user accounts so OU-based filtering should be fine.