They would be the first birds to fly there.
D and then if that doesn't work B. If you have anything else to ask me further about my answer (cause I have got to admit it is quite vague) just ask.
Hope this helps :) x
Answer:
A. Einstein's theory led scientists to discover black holes.
B. Thinking of space as blanket-like changed how scientists viewed gravity.
D. Newton and Einstein both had theories about gravity that worked.
Explanation: