What characterizes a fixed pulley?

A fixed pulley is characterized by being attached to a fixed structure, which means it does not move with the load being lifted. This setup allows the pulley to change the direction of the force applied, making it easier to lift an object by pulling down on the rope or cable.

Although fixed pulleys can help with lifting, they do not provide a mechanical advantage in terms of reducing the effort needed to lift a load; the effort required is generally equal to the weight of the load. Therefore, while a fixed pulley is indeed useful, its primary characteristic is its fixed attachment point, making option C the most accurate description.

The other options incorrectly attribute features to the fixed pulley that don't align with its fundamental properties. For example, moving with the load pertains more to movable pulleys, while mechanical advantage relates to combinations of pulleys or block systems rather than a single fixed pulley. Lastly, saying it is used primarily for heavy objects doesn't accurately reflect its use because fixed pulleys can be used for a variety of loads, not just heavy ones.