The worst single event of the great stock market crash of 1929 was
Explanation:
<em><u>The worst single event of the great stock market crash of 1929 was</u></em> <u>that quotes plummeted due to a massive sale of shares by the Curb Exchange</u> - <em><u>now called American Stock Exchange</u></em> - <u>of the well-known firm Cities Service Co</u>.