Which would best reduce the amount of energy needed to pull a wagon up a ramp?
1.increasing the slope of the ramp
2.reducing the friction between the wagon wheels
3.reducing the length of the wagon handle
4.increasing the friction between the wagon wheels

2.Reducing the friction between the wagon wheels

Explanation:

If the friction between the wagon wheels and the rail is reduced, then less force will be needed to pull the wagon up. This is because the friction force goes in the opposite direction of the movement, that is, friction force opposes the desired movement, making it more difficult.

where are the vectors ?

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.