A book is sitting on a desk. What best describes the normal force acting on the book? the upward force the desk pushes on the book
the upward force the book pulls on the Earth
the downward force the book pushes on the desk
the downward force the Earth pulls on the book

Explanation:

in my opinion I'd say it's gravity because it's making the book stay in it's one and only position pulling the book at the center of the desk

compass can be used day and night, cloudy or sunny

the components of a vector are the parts of the vectors that are to each other.

b perpendicular