We’re looking for an example of some outside, overlooked force that affected a prediction. But scientists tried to predict Uranus’s orbit, making Uranus the focus of a prediction, rather than a disturbing force that affected that prediction.

Author A suggests disturbing forces are those that are overlooked or unaccounted for. When making predictions, she says, scientists need to assume that any such forces aren’t going to mess with their predictions. But in passage B, scientists accounted for the sun. It wasn’t an unexpected factor that messed anything up. So it’s not a good example of a disturbing force.

Author A says that to derive a prediction from a theory, scientists need to assume the absence of disturbing forces. That is, they need to assume other forces out there in the world aren’t going to mess with the prediction. Author B then says that when scientists tried to predict Uranus’s orbit, they overlooked Neptune’s force of gravity, which messed with their prediction. So Neptune was a disturbing force.

We’re looking for an example of some outside, overlooked force that affected a prediction. But scientists tried to predict Mercury’s orbit, making Mercury the focus of a prediction, rather than a disturbing force that affected that prediction.

The moon isn’t mentioned in passage B, so it can’t be an illustration of anything.