The following extract is from a children’s school science book. Read it and answer question.

When houses are double glazed, only a relatively small amount of heat is lost through the windows. Double glazed windows have two panes of glass and are strapped between them, preventing escaping of the heat. Double glazing also ensures that condensation is reduced and noise is decreased. Heating bills can be reduced when double glazing is installed. People living near busy roads or airports also find that double glazing has to be fitted.

(Taken from Exploring Grammar in Context – Cambridge University Press)