What prevented the Europeans from colonizing Africa before the nineteenth century?

Why were entrepreneurs able to earn such good profits in businesses related to the california gold rush? a.) it was very difficult for entrepreneurs to earn any profit in businesses related to the california gold rush. most went broke and headed back east. b.) supplies were scarce and demand was great. entrepreneurs provided the things the miners needed. that allowed the entrepreneurs to earn good profits. c.) when the state of california noticed the high profits the entrepreneurs were making, it took over their private businesses. the state earned all of the profits after that. d.) a small group formed. it would not allow other entrepreneurs to open businesses. bykeeping the supply of goods low, the group was able to earn very high profits.