In which state is Earths outer core believed to exist?

Correct answer: Liquid

The direct answer is D, liquid. Earth’s outer core is believed to be a very hot, fluid layer made mainly of iron and nickel. Scientists infer this from earthquake-wave behaviour: S waves cannot travel through liquids, and they do not pass through the outer core. P waves can travel through it but change speed and direction. The outer core is different from the inner core, which is solid because of enormous pressure despite its high temperature. Option A, solid, describes the inner core more accurately, not the outer core. Option B, gaseous, is wrong because the core is compressed metal, not gas. Option C, plasma, is not the school-level physical state used for the outer core; it is not described as a freely ionized gas layer in this context. Option D is correct because seismic evidence supports a liquid outer core. Reasoning: S-wave shadow zone and P-wave changes → outer core is fluid. Memory cue: outer core flows; inner core is firm.