A newly discovered painting on wooden panel by Michelangelo must have been completed after 1507 but before 1509. It cannot have been painted earlier than 1507 because one of its central figures carries a coin that was not minted until that year. It cannot have been painted after 1509 because it contains a pigment that Michelangelo is known to have abandoned when a cheaper alternative became available in that year.
Which of the following is an assumption on which the argument depends?
- No stocks of the abandoned pigment existed after 1509.
- Michelangelo did not work on the painting over the course of several years.
- The coin depicted in the painting was known to general public in 1507.
- The wooden panel on which the painting was executed cannot be tested accurately for age.
- Michelangelo's painting style did not change between 1507 and 1509.
I find A and B to be equally strong assumptions. The explaination mentioned below wasnt convincing. Its required to make sure that Michelanglo has no stocks of the abandoned pigment after 1509. Otherwise he would have the used old stock to finish the painting in a year after 1509.
Does this mean B is the stronger choice? Did i completely miss something or is there a better way to pick the right answer?
Choice A is incorrect. We do not need to assume that no stocks of the pigment existed after 1509. The argument is concerned only with the year in which Michelangelo stopped using the pigment.
Choice B is correct. In order to conclude that the painting must have been completed before 1509 on the basis of the pigment, we must assume that he did not begin the painting before 1509 using the old pigment and complete the painting after 1509 with the new pigment.