It is called the reaction force of a bird flying.
I'm pretty sure its d. because depends what tipe of dog it is there are some that see different colors so I'm pretty sure its d.
I think their distance is a measurement of : B. space in two dimension
In two-dimensional space, both directions located in the same plane , and the distance in locations only separated by width and length (there is no volume in this model)
It's difficult to measure that because it's hard to make sure it is only a uniform layer of gas in whatever you're measuring it in
