Exam 70-347 topic 4 question 23 discussion

You are the Office 365 administrator for your company. The company allows external communications through Microsoft Lync Online for all domains.
The call center manager reports that call center personnel are spending too much time chatting with friends and not enough time taking calls. She requests that the call center personnel be blocked from chatting with anyone external to the company by using Lync Online. They still must be able to communicate with internal users.
You need to prevent all call center personnel from communicating with external contacts by using Lync Online, while still allowing other employees to communicate with external contacts.
What should you do?

Suggested Answer: D 🗳️
The question states that "You need to prevent all call center personnel from communicating with external contacts by using Lync Online, while still allowing other employees to communicate with external contacts." Therefore, we need to apply the restriction to the call center personnel only.
The question also states that "They still must be able to communicate with internal users."
You can turn off external messaging for a single user by clearing the People on Public IM Networks check box. This will override the company setting of allowing external access. The image below shows the People on Public IM Networks check box.
To ensure that the call center personnel can continue to be able to communicate with internal users, we need to leave the Lync users checkbox ticked.