Which was a major effect of the european slave trade on africa?

a) the spread of islam was halted.
b) it led to rapid decrease in tribal warfare.
c) the decline of african kingdoms accelerated.
d) it led to stronger economic systems in africa.

How did the construction of the erie canal improve transportation in the united states in the 1820s? a. the canal connected the great lakes to the mississippi river. b. the canal connected the great lakes to the ohio river. c. the canal connected the atlantic and pacific oceans. d. the canal connected the great lakes to the atlantic ocean.