How can seismic waves be used to determine an earthquakes

How many variables are altered in a good experiment? a.1 b.0 c.2 d.3

1) what three conditions must be present for minerals to form through natural processes? 2) why are minerals considered inorganic substances? 3) how do oxides differ from other minerals that contain oxygen atoms? 4) how is a sulfide different from a sulfate? what makes native elements unique?

If a strand of dna has 35% thymine. what is the percentage of cytosine, adenine, guanine?