A recent survey revealed that the proportion of stage artists belonging to Theatreville that visited skin specialists for treatment related to skin lesions has increased significantly over the past ten years. As a part of their jobs, stage artists typically use make-up containing lead, the main culprit behind such skin lesions. Therefore, either the artists are using unusually higher amount of make-up or they have more sensitive skins than the artists had a decade ago.

Which of the following is an assumption on which the argument depends?

A) There has not been any significant increase in the number of stage artists in Theatreville.
B) The make-up kits that most artists have been using now do not achieve long-lasting make-up effects by significantly increasing the concentration of lead.
C) No other ingredient in the make-up used by the stage artists is responsible for other skin irritations for which a visit to the doctor is required.
D) People with highly sensitive skins are likely to be vulnerable to the side effects of lead used in the make-up.
E) Some companies have introduced high quality make-up in which the composition does not require the inclusion of high quantities of lead-based substances