O-LevelBiologyEcology & Environment5090/12 · May/June 2015 · Q301 Mark

How do nitrogen-fixing bacteria improve soil fertility?

AThey convert nitrates to nitrites.

BThey convert nitrites to nitrates.

CThey release nitrogen gas from nitrates.

DThey use nitrogen gas to make nitrogen-containing compounds.

✓ Correct answer

D: They use nitrogen gas to make nitrogen-containing compounds.

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Topic: Ecology & Environment, O-Level Biology (syllabus 5090). Multiple choice, 1 mark.
Source: O-Level Biology, May/June 2015 Paper 1 Variant 2, question 30.

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