Answer:
I would say A or C.
Step-by-step explanation:
Reason to why not B and D: The "big years" is not about finding the most birds so I'm not sure why the author would want to imply that the records can easily be broken/are meant to be broken.
Not to mention a quote from the text is "..winner managed to see 744 birds in one year"
Thats a lotta birds.
I'm doing the test right now but I wanted to help, ima go with A and if its wrong I'll give you guys an update.
EDIT: Okay its A! I turned it in and I was right! :)