What is the primary characteristic of profile drag?

The primary characteristic of profile drag is that it is experienced by all moving objects in airflow. Profile drag, also known as induced drag or form drag, results from the shape of an object as it moves through the air, causing air resistance. Almost every object that is in motion through a fluid, including air, will encounter this type of drag due to its surface area and shape, which disrupts the airflow around it.

In contrast, the other options suggest conditions or characteristics that do not encompass the fundamental nature of profile drag. For instance, drag does not necessarily decrease with altitude since factors like air density interact with other types of drag differently. Profile drag does not cause lift; rather, lift is a separate aerodynamic phenomenon. Lastly, profile drag exists at various speeds, including low and high, rather than being restricted to just high speeds. Therefore, the correct understanding of profile drag is that it is universally present in all moving objects subjected to airflow.