How do scientists know about the structure of the earth? Question 21 options:

We have drilled all the way to the core of the earth.

We have drilled far enough into the earth to reach the mantle.

S waves from earthquakes can travel through both solids and liquids so they tell us what is inside the earth.

P waves from earthquakes can travel through both solids and liquids so they tell us what is inside the earth.

Asample of digestive juice was removed from the stomach of a pig. the juice was placed in a test tube along with some grains of wheat. a second test tube was set up containing an equal number of wheat grains, with distilled water rather than digestive juice. the test tubes were kept for 8 hours at 40 degrees c. after 8 hours, the grains inside the digestive juice had broken into tiny particles. the grains of wheat, in the water, were wet but otherwise unchanged. what is the control group?