Answer and explanation: Just as the organs in an organ system work together to accomplish their task, so the different organ systems also cooperate to keep the body running. For example, the respiratory system and the circulatory system work closely together to deliver oxygen to cells and to get rid of the carbon dioxide the cells produce.
Answer: There is not work done at the door because the door did not move.
Explanation: Work is defined as the movement done by a force.
So if you move to apply a force F in an object and you move it a distance D, the work applied on the object is
W = F*D
In this case, the secret agent pushes against the door, so there is a force, but the agent does not move the door, so D = 0, so there is no motion of the door, which implies that there is no work done at the door.
B. only its velocity should change
