Multiple choice

Over millions of years, the _____ of salt in the ocean has increased to about 3.5%.

  1. natural resources

  2. amount

  3. concentration

  4. evaporation

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Concentration refers to the amount of a substance (in this case, salt) per unit volume of a solution (the ocean water). Over time, evaporation has concentrated the salts in the ocean.