In developed countries, such as Canada, the percentage of the population diagnosed with clinical depression is much greater than that in developing countries. Researchers hypothesize that this difference is due to the increased leisure time afforded to residents of developed countries.

The hypothesis of the researchers depends on which of the following assumptions?

(A) Clinical depression is a genetically transmitted malady.
(B) Access to accurate diagnostic procedures for depression is equal for residents of developing and developed countries.
(C) Most activities characterized as "leisure time" in developed countries are inherently boring.
(D) Certain medications that effectively treat clinical depression are not readily available in developing countries.
(E) Few residents of developing countries dedicate any of their time to leisure.