Can someone help me please and thanks

For a comparative or experimental investigation, scientists often make a testable about a scientific question, and then they test it in the investigation. a.control b.hypothesis c.procedure d.system

This is collection of data made by comparing objects in standard units. in science, the units are metric.

Which gas prevents the spread of fire and extinguishes it? is a type of compressed gas that prevents the spread of fire and extinguishes it.