Smallest city in South America
It's C. The removal of water from aquifers.
Increasing wavelength is an indication of a Doppler shift caused by an object moving away from the viewer. Longer wavelengths (of the visible spectrum) are redder, shorter wavelengths are bluer. Objects moving away from you have a red shift, objects moving toward you have a blue shift.
La característica en común es que esos países subdesarrollados concentran la mayor cantidad de empleos en el sector terciario o de servicios. Espero que te ayude!