Melissa, Jessica, Sandy and Nicole were working on the computer. Suddenly, I heard a crash and then lots of shouts. I rushed in to find out what was going on, finding the computer monitor on the ground, surrounded with broken glass! Sandy and Jessica spoke almost at the same time:
Jessica said, “It wasn’t me!”
Sandy said, “It was Nicole!”
Melissa said, “No, it was Sandy!”
Nicole said, “Sandy’s a liar.”
Only one of them was telling the truth, so who broke the monitor?
Jessica broke the monitor. Nicole was telling the truth.
Only one of them was telling the truth, that means that the other three were lying.
If Sandy did it, both Jessica and Melissa will be telling the truth.
If Melissa did it, both Jessica and Nicole will be telling the truth.
If Nicole did it, both Jessica and Sandy will be telling the truth.
If Jessica did it, only Nicole will be telling the truth.