Hello Boris
The question as it is stated is not very clear. After doing a search, I found that the question you stated is used as a summary. The specific question that is being asked is:
The enterprise network WAN link has been receiving several denial of service attacks from both IPv4 and IPv6 sources. Which three elements can you use to identify an IPv6 packet via its header, in order to filter future attacks? (Choose three.)
The question is specifically asking you to show how you would distinguish an IPv6 header from an IPv4 header. The answers are: Traffic Class, Flow Label, and Hop Limit as these headers are only found in IPv6 headers.
I hope this has been helpful!
Laz