过去一年里，她的英语水平一直停滞不前。

Her English level has ___flatlined for the past year.

心电监护仪显示病人的心电图已经呈一条直线。

The ECG monitor showed the patient's heart had ___flatlined.

我讲了个笑话想活跃气氛，但他完全没反应。

I told a joke to lighten the mood, but he totally ___flatlined.

尽管老师讲得很生动，但全班同学依然毫无反应。

The whole class ___flatlined even though the teacher gave an exciting lecture.