A scientist is conducting an investigation that involves water, silver, carbon dioxide, and oxygen gas.

Which group of statements best describe all of the materials he is using in the investigation?

The best description is provided by the statement:

They are all matter. Some are compounds made of one type of element. Some are pure elements.

Matter is defined as any substance that has mass and takes up a space (volume). Water and carbon dioxide are compounds made of different elements, while silver and oxygen are pure elements.