4. You are looking at a layer of rock. The rock contains a fossil seashell. How do you know that this area of land was once covered by an ocean?

answer; /// i believe that the correct answer is (50%);

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added