牙医可能会决定拔掉那颗牙，以免反复发作。A dentist may decide to extract the tooth to prevent recurrent trouble.他死于劳累过度引起的心脏病发作。He died of a heart attack brought on by overwork.新药减轻了肺炎发作时的痛苦。The new drug lessens the severity of pneumonia epi...
它只在静脉里起作用，在静脉中血液流动更慢一些。It works only in the veins, where the blood flow is slower.早产婴儿必须靠静脉输入喂养。Premature babies have to be fed intravenously.长途航班上的乘客须注意可能出现深静脉血栓。Passengers on long-haul flights are being warned about th...