What event occurred on Black Tuesday?

AUnemployment reached nearly 25 percent.
BThe Federal Reserve lowered interest rates.
CInvestors sold more than 16 million shares of stock.
DGermany stopped reparation payments to the United States

Verified Answer :

C). Investors sold more than 16 million shares of stock . . . about 4 times the average amount . . . on October 29, 1929 . . . marking the financial beginning of The Great Depression (USA)

CInvestors sold more than 16 million shares of stocks