Who did hitler reach a secret agreement with before invading poland

What would lead a historian to consider two events to have a relationship of correlation rather than causation?

Which is the main inference that can be drawn from adam smith's book the wealth of nations? a) for an economy to work flawlessly, it shouldn't have to serve and moral goals.b) the government must control a free-market economy, or economic problems will arise.c) a free-market economy works well only without the government's interference. d) free trade will only hurt economies and should be stopped by governments.

When did the us congress declare war on the confederate states?