Which of the following factors determines how harmful an introduced chemical will be on the environment?

What is the difference between external & internal migration

What did the pattern of earthquakes in the wadati-benioff seafloor zones show scientists? a.) earthquakes occur where the ocean floor reaches its highest temperatures. b.) many earthquakes take place 700 kilometers below the seafloor. c.) slabs of ocean floor return to the mantle in subduction zones. d.) ocean - trenches cause earthquakes.

Find the coordinates of a if b(-9,-10) is the midpoint of ac and c has the coordinates of (-1,9)