Jiang is a network engineer for an enterprise organization. The company recently implemented a new unified communications $($UC$).$ platform. In preparation, Jiang's group made several network improvements, including a big increase in bandwidth. However, some users have reported poor$-$quality experiences when participating in audio and video conferences. What is the most likely reason?

Network visibility is poor and monitoring tools cannot detect endpoint issues.

Access controls are too restrictive.

Network security is not strong enough.

The quality of some endpoints, such as computers and mobile devices, is low.