The answer is C,<span> The sum of all forces acting on the object is zero. hope that helps!!</span>
Cellphones use radio frequency waves to transmit sound through the speaker and the microphone.<span> The radio frequency energy that is given off by cell phones is a type of electromagnetic energy.
I hope I helped! =D</span>
Light travelling in a vacuum is the fastest thing in the universe. The speed would be 2.99x10^8 m/s. The answer to this question is 'vacuum', where light can travel the fastest. I hope this helps you. You're welcome!