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.

气球在阳光下慢慢膨胀。

The balloon is ___expanding slowly in the sunlight.

演讲者不断扩展他的论点，使其更加详细全面。

The speaker kept ___expanding his argument to make it more thorough.