You are presented with the question "What in the Earth's crust causes earthquakes?" and the following answer choices: 
- heat
 - stress
 - cracks
 - volcanoes
 - erosion
 - waves
 - Wind
 - Movement

Now knowing that faulting of rock in Earth 's crust causes earthquakes and faults are produced by stress in the earth's crust that either compress or extend rocks, choose the best answer.


 

  stress       