这部电影的英文字幕帮助我理解了对话。

The English ___subtitles in this movie helped me follow the dialogue.

这篇论文的主标题是'气候变化'，副标题是'21世纪的环境挑战'。

The article's main title is 'Climate Change' with the ___sub-title 'Environmental Challenges in the 21st Century'.