单选题 The lady in this strange tale very obviously suffers from a serious mental illness. Her plot against a completely innocent old man is a clear sign of ______.
【正确答案】 C
【答案解析】insanity精神失常；impulse冲动；disposition气质；天性，性情，如：a cheerful disposition开朗的性情；inspiration灵感，激励。句意：在这个性异的故事里，这位女士显然患一种严重的精神病。她对一名完全无辜的老妇人设计死亡是她精神失常的表现。