Several sources of labor were tried before african slavery became popular in the american south. which of the following was one of the main reasons for the popularity of african slavery?

using convict labor was seen as an immoral, uncivilized practice.
white people could not withstand working in the hot southern climate.
the cost of a white man's labor for 10 years could buy an african for life.
there were not enough native americans for the amount of work to be done.