السؤال 79

Which sentence contains a word-order error in the must-be versus can't-be present-deduction contrast?

The river gauge is rising quickly, so snow must be melting upstream.
The tyres are spotless, so this can't be the van used on the muddy track.
The voice is completely different, so the caller must be not our usual supplier.الإجابة الصحيحة
The only lit window is hers, so Priya must be awake in the attic room.

الشرح

The sentence about the caller is erroneous because must be not is not the standard negative-deduction pattern. Since the voice is demonstrably different, can't be gives the required confident negative inference.

الشرح

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