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Question #46582
The Question
A crop field is continuously irrigated with the effluent from a sewage treatment plant where the secondary treatment (aeration tank) has completely failed. Over time, the crops exhibit severe phosphorus deficiency, even though soil tests reveal abundant insoluble phosphorus. Which of the following represents the most accurate ecological and physiological cascade responsible for this condition?
Options
- A.
The high biochemical oxygen demand (BOD) of the effluent directly inhibits the active transport of phosphate ions by the root epidermal cells.
- B.
Failure of floc formation prevents the mineralization of organic nitrogen into ammonia, starving nitrifying bacteria; the resulting nitrogen deficiency in plants impairs root metabolism and the maintenance of obligate mycorrhizal associations necessary for phosphorus absorption.
- C.
The absence of anaerobic sludge digestion prevents the release of phosphorus-solubilizing enzymes into the effluent, rendering soil phosphorus immobile.
- D.
Unoxidized organic matter promotes the overgrowth of Nitrobacter, which rapidly converts available soil phosphorus into insoluble polyphosphates.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Activated Sludge Inoculum|Mycorrhiza Nutrient Dynamics|Decomposition Rate Modifiers
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often view nutrient cycles (Nitrogen and Phosphorus) in isolation.
The trap is failing to recognize that the biological mobilization of Phosphorus (via Mycorrhizae) is an energy-dependent symbiotic process that requires a healthy, Nitrogen-replete host plant.
The question tests the ability to link a failure in an anthropogenic microbial process (Activated Sludge) to a downstream ecological bottleneck (Nitrification) and a subsequent symbiotic collapse (Mycorrhizal failure).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Microbes in Human Welfare - Class 12 |
| Concept | Activated Sludge Inoculum |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |