Which one of the following crops is correctly matched with deep effective root zone (about 90–150 cm)?

Correct option is D

· classify cotton among deep-rooting crops (effective root zone about 90–150 cm), along with crops like alfalfa and wheat.
· Deep root systems allow cotton to extract water from deeper layers, making it better adapted to moderate soil moisture deficits.
Why other options are wrong
· (a) Onion – listed as a shallow-rooted vegetable, with typical root depth about 0.3–0.6 m.
· (b) Potato – has a shallow to moderately shallow root system, often around 0.4 m effective depth.
· (c) Rice – in most lowland conditions rice has relatively shallow roots (≈0.6 m or less effective depth), not 90–150 cm.