6. one of the main reasons for the 1929 stock market crash was that
a) stock prices had been too tightly controlled by the government.
b) too few people had been allowed to borrow money to pay for stocks
c) investors had not been allowed to borrow money to pay for stocks.
d) stock prices had risen too high because of speculation.

The best and most correct answer among the choices provided by the question is the fourth choice "Stock prices had risen too high because of speculation. "

The stock market crash of 1929 was not the sole cause of the Great Depression, but it did act to accelerate the global economic collapse of which it was also a symptom. By 1933, nearly half of America's banks had failed, and unemployment was approaching 15 million people, or 30 percent of the workforce.

I hope my answer has come to your help. God bless and have a nice day ahead!