Concept:Logical sequencing of sentences in a paragraph requires a clear introduction of the topic, followed by background, elaboration, example, and conclusion.
Explanation:Sentence 3 defines keystone species and their role – it opens the paragraph.
Sentence 2 gives historical origin by referring to ecologist Robert Paine – it logically follows the definition.
Sentence 5 uses “This idea” to link directly to Paine’s work – it explains the impact of the concept.
Sentence 4 provides a concrete example (sea otters and kelp forests) – it illustrates the idea.
Sentence 1 states the consequence of losing keystone species – it serves as a strong conclusion.
Options A, C, and D do not maintain this logical flow. For instance, starting with example (option C) or consequence (option D) disrupts coherence.
Answer:Option B (3-2-5-4-1)