他的声音如此单调，以至于让每个人都睡着了。

His voice was so ___monotonous that it put everyone to sleep.

工厂装配线通常涉及单调的任务。

Factory assembly lines often involve ___monotonous tasks.

演讲者的声音单调，缺乏任何节奏或变化。

The speaker's voice is ___monotonous and lacks any rhythm or modulation.