Tutor-visible context
Student context
Problem context
句子的真正主语是单数，虽然旁边有一个复数名词；需要说明主语和动词怎样对应。
Learning objective
检查学生的句子，指出主谓一致错误，而不是直接认可它。
Context window
Conversation history
No prior conversation. This case starts with the current student message.
Public boundary
What this page does not expose
This public development artifact intentionally excludes ground truth answers, known-misconception annotations, rubrics, and evaluator-only evidence. A future hidden challenge dataset must use the same fail-closed serialization boundary.