我们讨论的主题是无家可归。

Our ___subject for discussion is homelessness.

她制作了一系列关于家庭关系主题的纪录片。

She has made a series of documentaries on the ___subject of family relationships.

她喜欢游泳和练习瑜伽。事实上，这是我们第一课的主题。

She likes swimming and practising yoga. In fact, this was the ___subject of our first lesson.