Which of the following statements is correct? Select one: O a. A new indication has been discovered for a drug that is already on the market. However, there is no proven evidence of its side effects. This has nothing to do with what theorists call the uncertainty hypothesis to explain Variations in Medical Practice. O b. The number of diagnostic tests prescribed by a physician to a patient who on a previous visit was only prescribed one drug is an exponent of the so-called "intensive margin" O c. The research done by Wennberg refers only to resource use rates, not their economic consequences. O d. None of the other answers is correct