Yet Another Next Generation (YANG) is a language which is only used to describe data models (structure). It is not XML or JSON.

In the 5GHz spectrum some of the channels used by 802.11 are subject to Dynamic Frequency Selection (DFS) requirements. This is due to our clients coexistence with other RF technologies such as Maritime, Aviation and Weather RADAR.
Dynamic Frequency Selection (DFS) is the process of detecting radar signals that must be protected against interference from 5.0 GHz (802.11a/h) radios, and upon detection switch ng the operating frequency of the 5.0 GHz (802.11a/h) radio to one that is not interfering with he radar systems.
Reference:
https://www.cisco.com/en/US/docs/routers/access/wireless/software/guide/RadioChannelDFS.pdf Although DFS helps reduce interference with radar systems but "DFS channels" refer to the
5GHz channels that require DFS check. In other words, DFS channels are channels that may interfere with radar signal. Therefore we should disable these DFS channels > Answer C is correct. UNII-2 (5.250-5.350 GHz and 5.470-5.725 GHz) which conta ns channels 52, 56, 60, 64,
100, 104, 108, 112, 116, 120, 124, 128, 132, 136, and 140 are permitted in the United States, but shared with radar systems. Therefore, APs operating on UNII-2 channels are required to use Dynamic Frequency Selection (DFS) to avoid interfering with radar signals. If an AP detects a radar signal, it must immediately stop using that channel and randomly pick a new channel.
Reference:
https://documentation.meraki.com/MR/WiFi Basics and Best Practices/Channel Planning Best P ractices