3. Evaluate the validity of the following statement and explain your reasoning. Once scientists believe something to be true, they will say so with 100%
certainty.

If the scientist makes a statement so it is 100 % valid.

Explanation:

Once scientists believe something to be true, they will say so with 100%  certainty. This statement is true because the statements of the scientist is not based on theories. Scientist make any statement after performing many experiments in order to verify the statement. So if the scientist will say about something with 100 percent certainty so it is considered as valid because the statement goes through from a number of experiments.

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.