a. The Montreal protocol is associated with the control of emission of Ozone-depleting substances
b. Methane and carbon dioxide are greenhouse gases
c. Dobson units are used to measure the oxygen content of air
d. Use of incinerators is crucial to disposal of hospital wastes
Answer: c. Dobson units are used to measure the oxygen content of air
Explanation: Dobson (DU) units are used to represent the concentration of ozone in our atmosphere. The amount of ozone is greater in the equator than in the poles.