If the Himalayas were formed by ductile rock deformation, then the Himalayas were formed by what?

Answer choices:
- fissures of hot, acidic water
 - Movement of an air mass
 - movements in the earth's crust
 - movement of tectonic plates
 - remains of prehistoric life
 - tectonic plates coliding
 - air mass over Earth's surface
 - ductile rock deformation

 

        ductile rock deformation  