他紧张地紧握着方向盘，手指都发白了。

He was ___clenching the steering wheel so tightly his knuckles turned white.

他在紧张时会不自觉地握紧拳头。

He keeps ___clenching his fists unconsciously when nervous.

她紧张时总是紧握拳头。

She keeps ___clenching her fists when she's nervous.