技巧: 将“doubtful”与“double”(双倍的)联系起来,想象面对两个选择时的犹豫和不确定性。可以通过构建类似“I feel doubtful when faced with double choices.”的句子来帮助记忆。
小故事
英文: John looked at the cloudy sky, feeling doubtful about whether to bring an umbrella. He didn't want to be caught unprepared, but also didn't want to carry it unnecessarily. In the end, he decided to take one just in case.