单选题
The writer became aware of her memory problem when she realized that she had ______.
【正确答案】
D
【答案解析】[精析] 细节题。文章第一段第一句说“It was the day I froze a household pet that I began to worry about my memory．”，且从下文可知这里的“household pet”指的是一袋热带鱼，可知作者是在发现自己将热带鱼放错时意识到她的记忆问题的。故选D。