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A non-defining relative clause adds extra information about an already identified noun and is set off by commas: This wetland, which stores floodwater, needs protection. Use who, which or whose, not that. Do not omit the relative pronoun. The sentence still identifies its subject if the clause is removed.
English rhythm often gives stronger beats to important nouns, main verbs, adjectives and adverbs. Short function words may be weaker: “BIRDS need CLEAN WAter.” Do not stress every syllable equally. The exact focus can change to show contrast, so listen to meaning as well as rhythm.