You need to ensure that users in both offices can transfer files by using Lync Online

You deploy Lync Online for a company that has offices in San Francisco and New York. The two
offices both connect to the Internet. There is no private network link between the offices.
Users in the New York office report that they cannot transfer files to the users in the San Francisco
office by using Lync Online.
You need to ensure that users in both offices can transfer files by using Lync Online.
What should you do?

A.
Configure the firewall to open Transmission Control Protocol (TCP) ports 50060-50079.

B.
Configure the firewall to open Transmission Control Protocol (TCP) ports 50040-50059.

C.
Create a private network connection to share files.

D.
Upgrade all of the Lync Online clients to use Lync 2013.