to overcome Earth's gravitational force to protect equipment from radiation to break through the sound barrier to avoid Earth's magnetic field
I gave my students this multiple choice question: Why do satellites and spacecraft launched from Earth need to reach a specific speed to escape Earth's surface?

Only one answer is correct among these 4 choices:
- to overcome Earth's gravitational force
- to protect equipment from radiation
- to break through the sound barrier
- to avoid Earth's magnetic field

Could you tell me which one is correct?

to overcome Earth's gravitational force