Do you agree with critics who charge that interest groups are harmful to the public good? explain

This is of course a somewhat subjective question, but most would agree that it depends entirely on what the interest group sets out to do, and whether the intentions of the special interest group hurt or further your own ideas of "right and wrong". 

many investors sold their shares or pulled their money out of the market

Explanation: During this period, production had declined and unemployment had risen, leaving stocks in great excess of their real value. Other causes of the crash include low wages, the proliferation of debt, a struggling agricultural sector and an excess of large bank loans that could not be liquidated.

With most investors selling their shares, billions of dollars were lost because the buyout was less than the actual value. Soon after the crash, people panicked and withdrew their money from the banks. While the crash was not the cause of the Depression, it was what triggered it as there were already weaknesses in the economy.