The __ variable is sometimes called the “manipulative ” because

Independent.

Explanation: The Independent variable is sometimes called the "manipulative" because it refers to a quantity that is changed by the experimenter.

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle

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.