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GS Paper IUPSC Prelims 2000
Health & Medicine
Question No. 393Interactive Test Mode
00:00
+2-0.66

Q393. Which one of the following organisms can serve as a biofertilizer for rice crops?

Which one of the following organisms can serve as a biofertilizer for rice crops?

Select the correct option below (or cross out options to eliminate)
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Official Answer Key & Detailed Solution

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Official UPSC Answer KeyUPSC Prelims 2000 • Science and Technology

Correct Answer: Option (A) — Blue-green algae

Concept & Option Breakdown

Standard Reference Verified
  • Blue-green algae (Cyanobacteria), such as Anabaena, Nostoc, and Anabaena azollae (associated with the water fern Azolla), thrive in waterlogged paddy fields and fix atmospheric nitrogen, acting as standard biofertilizers for lowland rice cultivation.
  • Rhizobium forms symbiotic root nodules primarily with leguminous crops, not rice.
Elimination Heuristic & Exam Approach

Rice is grown in flooded paddy fields—blue-green algae and Azolla are the specific biofertilizers adapted to waterlogged wetland conditions.

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Question Specifications & Syllabus Mapping

Examination & YearUPSC Civil Services Preliminary Examination 2000 (Q393)
Paper & Marking SchemeGS Paper I • 2 Marks (-0.66 Negative for incorrect response)
Syllabus Subject & TopicScience and Technology → Health & Medicine
Official Answer KeyOption (A) — Blue-green algae

Related & Repeated Prelims PYQs (4)

Questions from other UPSC Prelims years testing the same or closely linked concept.

View Cluster in 3D Graph
2013 • Q22586% Match

Consider the following organisms: 1. Agaricus 2. Nostoc 3. Spirogyra Which of the above is/are used as biofertilizer/biofertilizers?

Environment and Ecology • Ecology & EcosystemsSolve
1999 • Q39785% Match

Which one of the following is a useful functional association between fungi and the roots of higher plants?

Science and Technology • Health & MedicineSolve
2010 • Q2180% Match

Genetically modified “golden rice” has been engineered to meet human nutritional requirements. Which one of the following statements best qualifies golden rice?

Science and Technology • Biotechnology & GeneticsSolve
1998 • Q39980% Match

Which one of the following types of micro organisms is most widely used in industries?

Science and Technology • Health & MedicineSolve

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Frequently Asked Questions — UPSC Prelims 2000 Q393

What is the official answer for UPSC Prelims 2000 GS Paper I Question 393 (Science and Technology)?

The official UPSC answer key for this 2000 Science and Technology (Health & Medicine) question is Option (A): "Blue-green algae". Correct attempts carry 2 Marks with -0.66 Negative penalty for wrong answers.

Which UPSC Prelims syllabus topic does this 2000 question belong to?

This question belongs to GS Paper I under the subject "Science and Technology" and micro-topic "Health & Medicine". You can explore all repeated questions from Health & Medicine in Acme AI's 3D Prelims PYQ Realm or practice 50 full-length and sectional tests in the APT Prelims Test Series.

How can I solve this Health & Medicine UPSC Prelims question using option elimination?

Rice is grown in flooded paddy fields—bluegreen algae and Azolla are the specific biofertilizers adapted to waterlogged wetland conditions.

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