Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Which situation would most likely cause an object to travel in a circular motion?
one force acting on the object perpendicular to the direction of the motion
An object attached to a string being twirled around in a plane.