I believe that finding the balance of drones would be putting a limit on how many drones a country can use at one time. I'm not sure on the other 2 questions.
Answer:
it removed Russia from the war and brought about the transformation of the Russian empire into the union of Soviet socialist republics.
Cyrus McCormick in 1831. This machine was used<span> by farmers to harvest crops mechanically. For hundreds of years, farmers and field workers had to harvest crops by hand using a sickle or other methods, which was an arduous task at best</span>
B. the world trade center and the twin towers and the Pentagon
