Final answer:
The net force on a book weighing 4N when held at rest in your hands is 0N, as per Newton's First Law of Motion. The forces acting upon it are balanced, resulting in no net force.
Step-by-step explanation:
The subject of your question is Physics, specifically relating to the concepts of force and gravity. When a book is held at rest in your hand, it is not moving or accelerating, meaning that the forces acting upon it are balanced. These forces include the weight of the book, which is the force due to gravity, and the upward force your hand exerts on the book. In this state of equilibrium, the net force on the book is zero Newton, which corresponds to choice (b). This is determined by Newton's First Law of Motion: an object at rest tends to stay at rest unless acted upon by an unbalanced force.
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