今天我们要学的词是undercover。 Undercover, 是指秘密的，暗中进行的。"An undercover operation," 就是一次秘密行动。最近，美国农业部宣布回收1亿4千3百万磅牛肉。"An undercover video showed that cows too sick to stand were slaughtered for human consumption," 因为一部秘密拍摄的录像显示，加州一家屠宰厂非法宰杀了很多病得站不起来的牛，并将牛肉送入市场。"The undercover investigator refused to disclose his identity for fear of retaliation," 因为担心报复，卧底拍摄录像的调查人员不肯透露自己的身份。好的，今天我们学习的词是undercover...