How did the growth of christianity and islam differ during the postclassical era? a. while christianity expanded in influence, the number of people who practiced islam decreased. b. while followers of christianity conquered nations to expand their numbers, islam did not spread beyond a regional religion. c. while christianity spread, europe became politically weaker; however, the islamic empire entered a golden age. d. while islam spread, mesopotamia experienced a decline in civilization; however, christianity entered a golden age.