They got to know with the photographs from the U - 2 spy plane.
<em>Hope this helped! :)</em>
Answer:
When nomadic pastoralists encroach on farmland their impact can be devastating for farmers. This is especially so on the marginal agricultural land on the frontier zones bordering the deserts. The grazing of herds can quickly reduce plant cover. This makes the soil unstable, and erosion soon follows
Germany was expected to pay $132 billion gold marks for war damages
B.
<span>The requirement that laundries be housed in brick buildings was an unfair burden on Chinese immigrants.</span>
