Which one of the following are pure substances : water, salt water, copper, brass, air, oxygen​

Copper, Water, and Oxygen

Explanation:

Because they are compounds and compounds are pure substances <3

copper

Explanation: because all of the atoms that make up copper are copper i.e its not a compound or mixture. not made od molecules

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.

answer; capital earns interest; entrepreneurship receives a profit or incurs a loss;