Mike: ‘You just can’t believe what they’ll think up next, can you?’
Jane: ‘There’s no saying.’
Correct answer: (c) There’s no saying.
Your answer was: [color=red]incorrect
Mike: ‘You just can’t believe what they’ll think up next, can you?’
Jane: ‘There’s no believing.’
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The idiom “there’s no saying” means that ‘it is not possible to anticipate or judge something’ or simply ‘it is not possible to say’.
I think yo’s explanation fits the first test sentence (Mike). “You just can’t believe what they’ll think up next” means that whenever they think something up, it’s hardly possible to believe what they’ve done or thought of doing. What they do is always so surprising/unexpected/unimaginable that you may well end up speechless.
Therefore, Jane’s response is to agree that it’s not possible to anticipate or imagine what they will do next: “There’s no saying (what they will do next).”
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