She sat up with a jerk.

她猛地坐了起来。

《牛津词典》

I found that 'knee-jerk' reaction curious, so I have a few questions and I'm hoping one of the naysayers will step up and answer them.

我对这种下意识的不假思索的反对颇为好奇，我想提几个问题并且希望这些反对者能够站出来回答这些问题。

youdao

He says people only turn up to watch him to see if he needs a "drool cup". He amusingly called a young voter who asked about his age a "little jerk".

他说人们来看他只是想瞧瞧他是否需要一只“口水杯.他将一位询问他年龄的青年选民戏称为“小傻瓜”。”

youdao

The pattern has been a steady rise when European news flow is minimal, followed by knee-jerk corrections when the debt crisis flares up.

FORBES: European Compromise Drives 4th Weekly Gain for U.S. Stocks

In one, he captures the experience of being from a "jerkwater" town: a village so small that steam-train crews had to "jerk" water up from streams or from people holding buckets along the tracks because there was no water tower from which to refill the engine.

WSJ: Hey, Who Are You Calling a Snob?

Libertarian activists need to set aside their decades-old knee-jerk reactions to the two major parties, roll up their sleeves, and make the Republican and Democratic parties more libertarian.

WSJ: Randy Barnett: The Mistake That Is the Libertarian Party