1．I often have a chat with my friends on ________ phone in my spare time.
【答案】the
【解析】句意为：在我闲暇时我经常和朋友们在电话里聊天。 on the phone是习惯搭配。故填the。
2．Health care workers are at risk of getting infectious diseases because of their exposure to patients.
【答案】the
【解析】句意为：医护人员有因接触病人而被感染的风险。at the risk of“冒着……风险”是固定搭配，故填the。
3．If you want to see a doctor，you fix a date with him ahead of time.That is common practice in the USA.
【答案】a
【解析】句意为：如果你想去看医生，你要提前和他约定日期。那在美国是一种惯例。a common practice意为“普遍的做法，惯例”，故填a。
