Which of the following was not a cause of the depression? a. mellon’s business-friendly tax policies enticed the rich into more frenzied stock market speculation. b. as consumer spending declined, the rate of investment in new factories and businesses also plummeted. c. the gold standard caused a tightening of currency supplies worldwide. d. corporate structures had been bloated by the success of the 1920s but were unprepared for the tightening of the economy. e. much of the profits that had been taken during the 1920s had been put back into companies rather than saved or invested in other ways.