Answer:
i think it's "I have found some proof that dragons may have existed."
D because the other answers use incorrect uses of your.
Answer: Depends..
Explanation: Could you provide the excerpt from the speech in question? You can do this through screenshot, comment, or editing the post. Doing so will help you effectively get the answers you need.
Hope this helps!
“the history of the English monarchy”
this topic is way too broad.