他深吸一口气，挺起胸膛。

He took a deep breath to expand his ___chest.

学校正在扩建操场以容纳更多学生。

The school is ___expanding the playground to accommodate more students.

请在报告中详细展开你的计划。

Please ___expand on your plan in the report.

经过这次旅行，他变得更加开朗健谈了。

After the trip, he started to ___expand more in conversations.