Work is done whenever a force or a component of a force results in a displacement. No component of the force is acting in the direction of motion when the book is moved horizontally with a constant velocity. The force and the displacement are independent.
B. It guarantees that separate branches of government have similar powers. Each branch controls its own policies and has its own regulations, but each branch have the power to keep the other two in check. It's a system know as Checks and Balances.
