500
Complete the text using the appropriate structures for expressing futurity:
They ... (try) to win until they ... (exhaust) all the possibilities and then they ... (it's possible they will) give up, but I believe it's more ... (they could) they will continue even though they ... (it's impossible for them) win.
They will be trying to win until they have exhausted all the possibilities and then they could/may give up, but I believe it's more likely/probable they will continue even though they can't win.