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.