Scientists use the theory of plate tectonics to understand the reasons volcanoes develop in certain locations. How does this show the validity of the theory?

A. The scientists are using observations.
B. The scientists are making predictions.
C. The scientists can see the plates moving beneath the volcano.
D. The scientists are repeating the experiments .

Which statement best describes the oxidation numbers of the atoms found in magnesium chloride? a. magnesium has a 2- oxidation number and chlorine has a 1+ oxidation number. b. magnesium has a 2- oxidation number and chlorine has a 2+ oxidation number. c. magnesium has a 2+ oxidation number and chlorine has a 1- oxidation number. d. magnesium has a 1+ oxidation number and chlorine has a 1- oxidation number.

Use the periodic table to determine the electron configuration of dysprosium (dy) and americium (am) in noble-gas notation.

The chart shows the bid provided by four contractors to complete a job. which contractor is the most cost-effective?