Why Was the Stock Market Crash of 1929 a Disaster

Why was the stock market crash of 1929 a disaster for the economy?

A) Through the "wealth effect," investors lost paper wealth and consequently ?reduced their spending on goods and services. This led to cutbacks in ?production and jobs.
B) Businessmen became pessimistic about the future and reduced spending on ?plants and equipment, thus causing reduced production and increased layoffs ?in the capital-goods sector of the economy.
C) The crash revealed a flawed structure of credit and weak system of banks ?and other financial institutions in the U.S.
D) All of the above are correct