Cream of tartar 酒石 , a weak acid, can be added to egg whites to help them foam泡沫 when they are beaten

Formerly , in the United States, many nurses worked as private duty nurses rather than in hospitals.

The first paper was made from the bark of the mulberry tree.

The megaphone(microphone) makes the voice sound louder because it points sound waves in one direction and keeps them from spreading out in all directions.

Some animals pant and sweat to speed evaporation of body moisture and thus cool themselves.