Without the actually predicted values in comparison to the real values it is only possible to give a very likely answer based on their scale: a) is 25 million off, which sounds bad but when compared to a few billion in population it's not even 1% b)3 billion is more than half the world population as error: very unlikely c)154 billion, unlikely that a prediction is off by a factor of ~30 d)same as c
so a) is most likely the solution, but in theory the predictions could be arbitrarily bad (things like negative population, or extreme growths)
