The IEEE 802.3bt standard, also known as PoE++ or 4PPoE, significantly increases the power available to end devices. It introduces two new types: Type 3 (up to 60W from the Power Sourcing Equipment - PSE) and Type 4 (up to 90W from the PSE). To manage these higher power levels, the standard extends the classification system defined in previous standards (802.3af/at). The 802.3bt standard defines power classes from 0 to 8. Class 8 is the highest, corresponding to Type 4 devices, and ensures a minimum of 71.3W of power is available at the Powered Device (PD).

B. Class 4 is the highest power class supported by the older IEEE 802.3at (PoE+) standard, not 802.3bt.

C. Class 1 is a valid, low-power class in all PoE standards but is not the highest class available.

D. 16 is not a valid power class defined by any of the IEEE 802.3 PoE standards.

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1. Official Vendor Documentation (CommScope/RUCKUS):

CommScope. (2020). Power over Ethernet (PoE) in the Enterprise. White Paper (WP-113260-EN). In the table "PoE standards at a glance" on page 3, it clearly shows that IEEE 802.3bt supports Classes 0-8 and delivers up to 71W at the PD for Class 8.

2. Peer-reviewed Academic Publications / Standards Body:

IEEE Std 802.3-2018, IEEE Standard for Ethernet, Section 10, Clause 145. "Type 3 and Type 4 Class and Type discovery, and power control". Table 145-1, "PD power classification," explicitly lists power classes 1 through 8, with Class 8 having a PClassPD range of > 60W to 71.3W.

3. University Courseware / Reputable Institutions:

University of New Hampshire InterOperability Laboratory (UNH-IOL). PoE Classes, Types, and Topologies. This resource, from a leading PoE testing and certification body, includes a table titled "PoE Standards" which specifies that IEEE 802.3bt-2018 includes Classes 5, 6, 7, and 8, with Class 8 being the maximum.