练习题 · 英文原题 · OC-TS-TST-09
Someone left the back gate open. It was Zara, Kai or Noah.
Zara says: "Kai did it."
Kai says: "I did not do it."
Noah says: "I did not do it."
Only one of the three children is telling the truth.
Who left the back gate open?
查看答案与解析(英文)
答案: C
Answer: C (Noah)
Try each child in turn and count how many sentences are true.
- If Zara did it: Kai's sentence and Noah's sentence are both true. That is two true sentences, so it was not Zara.
- If Kai did it: Zara's sentence and Noah's sentence are both true. Two again, so it was not Kai.
- If Noah did it: Zara's sentence is false, Kai's is true and Noah's is false. Exactly one is true, which matches. So Noah left the gate open.
Why the other options are wrong
- A (Kai): Zara's sentence points at Kai, but if Kai did it, Zara and Noah would both be telling the truth.
- B (It cannot be worked out.): Testing each child shows that exactly one of them fits, so it can be worked out.
- D (Zara): If Zara did it, both Kai and Noah would be telling the truth, which is two children, not one.

