Final answer:
Surface drag refers to the resistance force on a moving object through a fluid and is correctly termed both viscous drag and skin friction. The correct answer to the question about what surface drag is also called is 'c. A & B'.
Step-by-step explanation:
Surface drag, which is a resistance force exerted on an object moving through a fluid such as water or air, can be referred to using two different terms. The correct answer to the question 'Surface drag is also called:' is c. A & B, meaning it is known as both viscous drag and skin friction. Viscous drag arises from the viscosity of the fluid, referring to the friction between layers of the fluid, while skin friction refers to the friction between the object's surface and the fluid through which it is moving.
When an object falls through a viscous fluid, three forces are at play: its weight, the viscous drag, and the buoyant force. Viscous drag, specifically, depends significantly on the object's velocity and can involve complex behaviors at different flow regimes and speeds. Athletes, such as swimmers and cyclists, often wear body suits to minimize this drag force and improve their performance in competitions.