The process involved in achieving Green hydrogen is

Green hydrogen is hydrogen gas produced by electrolysis of water using electricity generated from a renewable source (solar, wind, or hydro power). In electrolysis, an electric current is passed through water, splitting it into hydrogen gas at the cathode and oxygen gas at the anode. Because the electricity comes from a renewable source, this hydrogen is produced with essentially zero associated carbon emissions, unlike hydrogen made from fossil fuels.

Applying this to the process named in the question: only Electrolysis matches this definition, since it is the process of passing electricity from a renewable source through water to split it into hydrogen and oxygen.

• Dehydrogenesis (dehydrogenation) removes hydrogen atoms from an existing hydrocarbon or organic compound; it does not split water using renewable electricity, so it does not describe the green-hydrogen route.

• Dehydration removes water content from a substance; it is a distinct physical/chemical process that produces no hydrogen gas at all.

• Since exactly one of the three named chemical processes matches the definition of green hydrogen production, an option claiming several processes qualify together, or that none of them qualifies, cannot be correct.

Hence, the process involved in achieving green hydrogen is Electrolysis.