What economic characteristic of the 1920s was a cause of the Great Depression?

high income tax rates
low tariffs on imported goods
overproduction of agricultural products
lack of available credit

I am between B and D i'm about 77 percent sure its B but the remaining 23 percent goes to D but i'm pretty sure the correct answer is B if not i'm sorry but im pretty sure its B because i remember this question slightly.

the conditions that made the byzantine empire vulnerable to attacks by the muslin turks were the sack of constantinople by western crusaders, the conquests of the sultanate of rum, presence of rival kingdoms and finally the set up of fiefdoms at the empire which were owned by the ghazis (turkish warriors).