In which scenario is tension present?

Tension is defined as a force that is transmitted through a string, rope, cable, or similar object that is being pulled tight by forces acting from opposite ends. In the case of muscles contracting and pulling on bones, this scenario perfectly embodies this definition. When muscles contract, they exert a pulling force on the tendons connected to bones, creating tension. This tension is what allows for movement and stability in the skeletal system, enabling activities such as lifting, walking, and running.

Tension is absent from scenarios where forces are exerting pressure in different ways. For example, in instances where weights push against each other, compression occurs rather than tension. Similarly, when an object's weight compresses a surface, it results in a compressive force, not tension. Lastly, in cases of unopposed rotational forces, while there may be forces at play, they do not generate tension as no pulling action through a medium is occurring.

Thus, the scenario that accurately represents the presence of tension is when muscles contract and pull on bones, making this the correct choice.