Key Concept: Different plant-parasitic nematodes are identified by the distinct symptom they cause.
Why it's correct: Meloidogyne incognita induces gall-like 'knots' on roots that block water and nutrient uptake, causing stunted growth — the textbook root-knot nematode.
Why others fail: Heterodera avenae causes cyst nematode disease, Pratylenchus penetrans causes root lesions, and Ditylenchus dipsaci attacks stems/bulbs — none of them produce root galls.