Critical Reasoning

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?

A) No stocks of the abandoned pigment existed after 1509.

B) Michelangelo did not work on the painting over the course of several years.

C) The coin depicted in the painting was known to general public in 1507.

D) The wooden panel on which the painting was executed cannot be tested accurately for age.

E) Michelangelo's painting style did not change between 1507 and 1509.

According to me this question isn't difficult.But the answer choices are unclear,more specifically,the correct answer bugs me.

Assumption is,according to me : The coin was not illegally in circulation prior to 1507 and the paint was not avaliable after 1509.

If this were to happen,you can't conclude that the painting was completed "after 1507 but before 1509"

Now I leave it upto you guys to select the answers.Please explain why you chose that answer.Experts,please hop in.