What is Black Tuesday and why does it mark the beginning of the Great Depression?

you basically answered your own question but OK.

Explanation:

October 29, 1929. On this date, share prices on the New York Stock Exchange completely collapsed, becoming a pivotal factor in the emergence of the Great Depression.

The DJIA fell 12%, one of the largest one-day drops in stock market history. More than 16 million shares were traded in the panic sell-off, which effectively ended the Roaring '20s and led the global economy into the Great Depression.

i don't know why don't you google it?

answer; /// i believe that the correct answer is (d)the huang he river valley;