1.1 A book lies on a table. This book is not moving because: A there are no forces acting on this book.
B the forces acting on the book are in equilibrium.
C the force that the table exerts on the book is greater than the force
that the Earth exerts on the book.
D the force that the book exerts on the Earth has the same magnitude
as the force that the Earth exerts on the book and therefore they
cancel.​

B The forces acting on the book are in equilibrium

Explanation:

The book that lies on the table and does not move according to Newton's First Law of motion, because there are no net forces acting on it, therefore the net force (the sum of forces acting on the book) is zero

Therefore, the magnitude of the forces acting on the book and the direction in which the forces acts on the balance each other such that the book is in an equilibrium state because the forces acting on the book (which can cause the book to move) are in equilibrium

Therefore, the book is not moving because the forces on the book are in equilibrium.

according to jean piaget, in what stage of cognitive development are children able to understand conservation task?

b. preoperational

just took it