On that list of choices, 'C' is the only "example" of a plane.
None of the choices "describes" a plane.
The amount of matter in an object is called its, mass. How much the mass weights would be referred to as weight
The duck at 12m/s has a greater speed than the heron which travels at 10m/s
The magnitude of gravity is expressed in terms of its acceleration. So the magnitude of ' g ' at that altitude is exactly 6.5 m/s^2.