A wave's frequency is 2 Hz and its wavelength is 4 m. What is the wave's speed?

Speed is distance over time, so v = λ / T. The frequency, f, is 1/T, so the equation relating wave speed, frequency, and wavelength is v = f λ .

Explanation:

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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.