I think the test question itself is weird, possibly because I don't really see 'carry on' used much in that kind of context in AE. We use it in the sense of 'make a fuss' ('He always carries on about high taxes'), and in the imperative, to encourage someone to keep working at a task or project, not to be distracted ('Carry on, don't mind me').
But to my ears, we don't really use it just in the sense of 'continue/keep doing something' (over and over). So we would be far more likely to say 'If you keep playing with that ball, ...'
In fact, the question sounds so weird to me that my original response to the prompt was to wonder whether they expected something like 'If you carry that ball outside where it belongs, you won't risk breaking something,' or 'If you carry that ball around in the house, you're going to drop it and break something.' But those don't make sense either, because a ball isn't a heavy load and just carrying it isn't looking for an accident to happen.
If they had really wanted 'carry on,' which is one syntactic unit, like a separable verb in German, I would have expected them to include both words in the prompt, not just 'carry' alone.