What geographic features created a barrier of people and goods in africa?

Ones to stop invaders

Explanation:

the correct answer is blue and green.

a visible spectrum is electromagnetic spectrum color that can be seen by a normal human being by a single wavelength of light. the visible light spectrum is the range of wavelengths that make up visible light. the visible light spectrum passes through a prism enabling the rainbow reveals all the colors in the spectrum. these range from red, orange, yellow, green, blue and violet.

answer at the divergent plate boundary in the middle of the ocean;