Our life and chemistry

The percentage of basic elements present in human body is

• oxygen (65 %), carbon (18%), Hydrogen (10%)

• oxygen (55 %), carbon (18%), Hydrogen (10%)

• oxygen (65 %), carbon (16%), Hydrogen (10%)

• oxygen (55 %), carbon (18%), Hydrogen (5%)

The respiration is the reverse process of

• allotropes

• breathing

• photosynthesis

• none of them

_________ is a naturally hardest materia

• diamond

• graphite

___________ is black in colour.

• Graphite

• diamond

_____________ is a bad conductor of electricity

• diamond

• graphite

____________ is opaque.

• graphite

• diamond

water freezes at _________ centigrade

• 0

• 4

water has maximum density at _________ centigrade.

• 0

• 4

__________________ is most abundant chemical compound

• carbon

• water

Fuel for combustion, coal, petroleum and gas use ________compounds.

• carbon

• Hydrogen