12.
there are two forces acting upon the book. the earth's gravitational pull exerts a downward force and the table pushes up on the book. since these two forces are of equal magnitude and in opposite directions, they each other.

a. balance
b. push against
c. slide past
d. focus

The Earth's gravitational pull and the table's force are of equal magnitude and in opposite directions, they balance each other.

Explanation:

A book placed on a surface have two forces acting on it which are, a force that pulls it toward the ground in a downward direction, that is gravitational pull and a second which is acted on the book on upward direction making a balance on the object.

This follows Newton’s third law of motion that states every action has an equal and opposite reaction.

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.