The normal level of CO2 in indoor air should be in the _____ of 400 - 600 parts per million.

A whale can slow down its heartbeat, which _____ it to stay underwater for longer.

_____ diamonds cost a lot less than the real thing.

On the Mars exploration robot are several _____ for measuring temperature, air quality and soil composition.

Researchers have discovered that rice was first _____ in China over 10,000 years ago .

_____ promises to reduce the size of electronic components to one-millionth of a meter.

The eggs of this fish _____ to plant leaves, so they do not get washed away.

An inert gas does not _____ directly with other materials.

Do not _____ a normal Google search to help you find academic sources; you also need to use the library database and Google Scholar.