Combustion and Flame

Write True/False against the following statements and also correct
the false statement.
(a) A physical process in which a substance reacts with oxygen
to give off heat is called combustion.
(b) Water is the best extinguisher for fires involving electrical
equipment.
(c) Alcohol, CNG and LPG are inflammable substances.
(d) Increased concentration of nitrogen in air is believed to cause
global warming.
(e) Greater the calorific value, better is the fuel.
(f) Middle zone is the hottest zone of a flame.
(g) The substances which vapourise during burning, give flame.