我忍不住打哈欠——我一定是累了。

I can't stop ___yawning - I must be tired.

视频显示学生们在数学课上打哈欠。

The video showed students ___yawning during the maths lesson.

无聊的讲座导致许多人公开打哈欠。

The boring lecture caused many people to ___yawn openly.