Ducks quack.

Quack, quack," said the duck.

The ducks quacked.

My mom thinks the doctor is a quack.

Quack, quack!" the duck said.

My cat quacks.

I'm a duck, quack. I speak English, quack.

In "A Journal of the Plague Year," a 1772 fictionalized account of London's Great Plague of 1665, Daniel Defoe notes that people were quick to turn to quacks and peddlers offering "Sovereign cordials against the corruption of the air."

The duck quacks 'quack quack'.

You listen more to what this quack says than what the doctor says.