What do you infer ‘We can only hope that this effort will spread to other cities as well’ in line 22-23
The author is not sure about the future of pollution control methods.
b. The author wishes to see other cities taking action to control air pollution.
c. The author doubts that effort to control pollution cannot be adopted by other cities.
d. The author doesn't want effort to control pollution to be spread in the other cities of the world.