1. The sound of the duck's quack echoed across the pond.
鸭子的嘎嘎叫声在池塘上回荡。

2. The self-proclaimed doctor turned out to be a quack, offering fake cures to desperate people.
这个自称医生的人原来是个江湖骗子，向绝望的人们兜售假药。

3. In the past, there used to be street vendors who would sell quack remedies made from duck eggs.
过去，曾经有街头小贩售卖用鸭蛋制成的假药。