When people interact in an effort to receive a reward or a return for their actions, a(n) has taken place.
a.
exchange
c.
barter
b.
division of labor
d.
both b and c

one part of the electromagnetic spectrum that arrives on earth as solar radiation from the sun is the visible spectrum. wavelengths of the visible spectrum combine to form what we refer to as

answer - d) ultraviolet radiation.

violet /   380–450 nm / 668–789 thz

violet is number 1 in the chart of visible light.