PLEASE NOTE b IS INCORRECT CAN YOU PLEASE GIVE ANOTHER ANSWER

Which of the following statements is correct?

Select one:

a. the use of tradeable permits and corrective taxes reduces the cost of environmental protection

b. rich countries usually have cleaner environments than poor countries because a clean environment is like other normal goods in that it has a positive income elasticity

c. clean water and clean air are goods to which the law of demand applies

d. all of the above are correct