语法总结
be going to 表示计划
is going to swim / set out 表示已有安排的将来动作。
相似句：
- We are going to leave tomorrow.
- She is going to take an exam.
who 引导非限制性定语从句
Debbie's mother, who swam... 补充说明母亲，逗号不能省略。
相似句：
- My uncle, who lives abroad, is visiting us.
- Tom, who won the race, smiled.