alleryRusting of iron requires the simultaneous presence of
AOnly oxygen
BOnly water
COnly hydrogen
DWater and oxygen
Answer & Solution
Correct answer: D. Water and oxygen
1. Rust is hydrated ferric oxide (Fe₂O₃·xH₂O).
2. Iron will not rust in dry air or air-free water.
3. Both moisture (H₂O) and oxygen (O₂) must be present.
4. This is why paint, oiling and galvanisation protect iron by keeping either component away.
_Source: syllabus Science, Ch 3 "Metals and Non-metals", §3.3_
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