Final answer:
In a typical high school physics problem, the gravitational force is likely the only force acting on a 2.0 kg body, as it is responsible for the attraction between two masses and is the dominant force at macroscopic scales.
Step-by-step explanation:
The only force acting on a 2.0 kg body could be any of the four fundamental forces depending on the context. However, in a typical high school physics problem where a body is not undergoing nuclear reactions or being considered at atomic or subatomic levels, the gravitational force is most likely the one being referred to. This force is responsible for the attraction between two masses and is described mathematically by Newton's law of universal gravitation, which states that the force is proportional to the product of the two masses and inversely proportional to the square of the distance between their centers.
On the other hand, the electromagnetic force is responsible for holding atoms and molecules together and is much stronger than gravity at atomic scales. The strong nuclear force is the force that holds the protons and neutrons together in an atomic nucleus and is the strongest of the four forces. Finally, the weak nuclear force is responsible for certain types of nuclear decay processes and is weaker than both the strong nuclear and electromagnetic forces but stronger than gravity. For macroscopic objects, gravity is typically the dominant force to consider unless other conditions are specified.