单选题 I've always been cautious about giving people my phone number.
  • A. afraid
  • B. frightened
  • C. careful
  • D. rational


【正确答案】 C
【答案解析】[解析] cautious和careful都表示“小心的、仔细的”；afraid：害怕的、担心的；frightened：受惊吓的、受恐吓的；rational：理性的、合理的。