What Roman engineering achievement made large public structures possible

In a planned economy, which of the following does the job of market forces in order to determine the outcomes?

Which of these statements describes a long-term impact of european imperialism in africa? a. african countries joined together to present a united front against imperialism. b. europeans paid african countries after colonizing them, offering these new countries a fresh start. c. european powers drew the current borders, splitting ethnic groups among modern countries. d. africans became more loyal to their countries than to their ethnic groups.

What specific events led richard nixon to resign the presidency