今天我们要学的词是 roll back. Roll back 意思是后退，退步。国际艾滋病大会星期天在华盛顿开幕，The participants called for governments not to roll back progress made against the epidemic even though they're facing tight budgets. 与会代表呼吁各国政府，虽然面临预算压力，也不要让打击艾滋病的进展退步。美联航上周五国内机票涨价，业界专家说，United could be forced to roll back the increase if other airlines don't match it soon. 如果其他航空公司不跟进的话，美联航可能会被迫将票价降低到涨价前的水平。好的，今天我们学习的词是 roll back, roll back, roll back....