Why did local phone companies have a natural monopoly before the arrival of cellular technology?

In 1933 the 21st amendment was added to the u.s. constitution, allowing for the manfacture, transportation, and sale of alacoholic beverages in the united states. why was this amendment needed?

Which of teh following would explain the importance of the trans-siberian railroad to russia's economy? (schoology test)

Many feel that the u.s. should not give money to the world bank to aid people in other countries. true or false