sparetime前面加什么介词

前面加介词in，例如：

1、He's studying music in his spare time.他在空闲时间学音乐。

2、Besides working as a doctor， he also writes novels in his spare time.除了当医生之外，他在业余时间还写小说。

3、In her spare time she does voluntary work她在业余时间做义工。