Answer the following question given this paragraph: Where do forces come from? Observations suggest that a force applied to an object is always applied by another object. A hammer strikes a nail, a car pulls a trailer, and a person pushes a grocery cart. Newton realized that forces are not so one-sided. When the hammer exerts a force on the nail, the nail also exerts a force on the hammerafter all, the hammer comes to rest after the interaction. This led to Newton's Third Law of Motion , which states that whenever one object exerts a force on a second object, the second object also exerts a force on the first object, equal in magnitude and opposite in direction. Q: Observations suggest that a force applied to an object is always applied by what? Choices: - itself - gravity - dark matter - another object A:
A:
another object