Which was not a cause of the great depression

Me i really need which of these was an accomplishment of the han dynasty? the invention of the seismograph finding a water passage to europe the invention of the ballpoint pen the invention of the abacus

What kind of contact did christopher columbus and native americans initially have?

What are your thoughts about " the attacking on the twin towers". in your own words a little paragraph its for a project i am doing and i want to get intel from other people so that i can put it on my poster. for anyone who gives me there opinion on it : ) enter you name when you type the paragraph more than one person to respond.