Where in the Layer 2 frame should this be verified?

A network engineer is configuring Cisco TrustSec and needs to ensure that the Security Group Tag is being transmitted between two devices.

Where in the Layer 2 frame should this be verified?
A . CMD filed
B . 802.1Q filed
C . Payload
D . 802.1 AE header

Answer: A

Explanation:

https://www.cisco.com/c/dam/global/en_ca/assets/ciscoconnect/2014/pdfs/policy_defined_segmentation_with_trustsec_rob_bleeker.pdf (slide 25)