Rearrange the following sentences to get a meaningful paragraph :

A. Hydrogen fuel cells produce electricity by introducing oxygen to mix with contained hydrogen, producing water as a byproduct. 

B. One way to obtain hydrogen is through the process of electrolysis, which uses electricity to split water into hydrogen and oxygen molecules.

C. The hydrogen is collected and contained for use or transport.

D. Hydrogen can play a big role in generating electricity.

Option D is the correct answer.

Sentence D introduces the topic by highlighting hydrogen's significant role in electricity generation, setting the stage for the discussion.

Sentence B logically follows by explaining how hydrogen can be obtained through the process of electrolysis, providing a foundation for understanding its sourcing.

Sentence C then describes the next step, where the collected hydrogen is contained for use or transport, creating a bridge between obtaining hydrogen and its practical application.

Finally, Sentence A concludes the flow by detailing how hydrogen fuel cells produce electricity, tying the explanation back to the topic introduced in Sentence D and completing the narrative cohesively.