State whether the following statements are true or false. If false, correct them.<br><b>(a)</b> Plants consume oxygen for respiration.<br><b>(b) </b>Plants produce oxygen during the process of making their own food.<br><b>(c)</b> Air helps in the movements of sailing yachts and gliders but plays no role in the flight of birds and aeroplanes.<br><b>(d)</b> Air does not occupy any space.