38. Where is the source of heat in a mantle convection currente
A. the core
B. the crust
C. the moon
D. the sun
39. Which of following is the region in which one plate moves under another
A. rift valley
B. subduction zone
C. magma chamber
D. vent
40 The motion of solid used by differences in temperature is called
A. plate tectonics
B. tectonic movement
C. magma chamber
D. convection current ​