一般过去时描述童年成长经历 — 英语选择题

Tom 写了一篇介绍自己成长经历的短文，其中有这样一句话："When I was six, I couldn't swim. Last year, when I was nine, I learned to swim." 根据这句话，下列哪一项是正确的？A. Tom can swim now. B. Tom learned to swim when he was six. C. Tom was tall when he was six. D. Tom learned to swim last month.