Which of the following is not used for putting out fires from electrical gadgets ?

• sand

• water

• foam

• carbon dioxide

Which of the following causes acid rain ?

• carbon dioxide

• sulphur dioxide

• carbon monoxide

• oxides of sulphur and nitrogen

The calorific value of fuel is expressed in

• joule

• kJ/kg

• kJ

• none of the above

The burning of candle is an example of

• spontaneous combustion

• rapid combustion

• slow oxidation

• explosion

The zone of the candle flame which is moderately hot is called

• non-luminous zone

• luminous zone

• inner dark zone

• lowest blue zone