Which of the following causes a precipitate to form?
a. atoms combining in a solution to form a solid
b. volcanoes erupting and magma cooling
c. lava crystallizing
d. minerals undergoing changes in pressure

Option (A) is the correct answer.

Explanation:

When in a chemical reaction, a liquid solution results in the formation of an insoluble solid then this solid is known as a precipitate.

For example,

Here solid formed is a precipitate as it remains insoluble in the reacting solution.

Hence, we can conclude that out of the given options atoms combining in a solution to form a solid causes a precipitate to form.

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.