6) The hardest substance available on earth is
A. Gold
B. Iron
C. Diamond
D. Platinum
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Answer Option C
7) Tetraethyl lead is used as
A. pain killer
B. fire extinguisher
C. mosquito repellent
D. petrol additive
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Answer Option D
8) The inert gas which is substituted for nitrogen in the air used by deep sea divers for breathing, is
A. Argon
B. Xenon
C. Helium
D. Krypton
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Answer Option C
9) The property of a substance to absorb moisture from the air on exposure is called
A. osmosis
B. deliquescence
C. efflorescence
D. desiccation
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Answer Option B
10) The average salinity of sea water is
A. 3%
B. 3.5%
C. 2.5%
D. 2%
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Answer Option B
 Questions in Competitive Examinations){kind=link}