检查车辆时，请先摆放好三角警示牌。

Before checking the vehicle, set up a ___warning ___triangle first.

这是一个三角形。

This is a ___triangle.

乐队里最小的女孩负责演奏三角铁。

The youngest girl in the band is playing the ___triangle.

他们之间的情感三角关系让周围的人都感到不适。

The emotional ___triangle between them made everyone around feel uncomfortable.