B.1- 
Clearly from the Residual error curve the degree of freedom for the nao robot is 3.
However actual degree of freedom is 2.
From a proper inspection of the images we can see that it has two degrees of freedom one about the elbow joint and one about shoulder joint , so only two angles are required are required to describe its position at any time.
B.2-
Clearly from the Residual error curve the degree of freedom for robotic agents is 2
However actual degree of freedom is 4.
Each agent has two arms and 2 angles are required to describe agent's position at any time, so we have a total 4 degrees of freedom (2 for each agent).
B.4-
Clearly from the Residual error curve the degree of freedom for robotic agents constrained to move a box horizontally is 1.
We can determine the state of system by any one angle because they are constrained to move the box horizontally by holding it at mid-point. Whereas in B.2 they were completely free to move but in B.4 they also have to hold the box at its mid-points so have lesser degrees of freedom.