We determine the distance of a Cepheid by We determine the distance of a Cepheid by measuring its parallax. knowing that all Cepheids have about the same luminosity and then applying the inverse square law for light. determining its luminosity from the period-luminosity relation and then applying the inverse square law for light.

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.

c) power lifting, will be your answer.

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