Stalin signed a nonaggression pact with Germany because he knew that Europe was on the brink of another major war, and he wanted time to be able to build up the Soviet military.
The answer is the first one, crime statistics of youth in cities that have curfews. If crime rates are lower, the curfew most likely works.
It said that as of January 1, 1863, all slaves in the rebellious states "shall be, thenceforward, and forever free." This was issued by Lincoln to preserve the nation into a battle for human freedom.
Honestly, none. The union didn't really have any agricultural advantages over the Confederacy, in fact, it can be argued that agriculture was one of the biggest disadvantages of the union.
