This question examines the examinee's understanding of psychological factors. Related to speculative factors is psychological factors, that is, speculators' confidence in the market. When people are full of confidence in the market, even if there is no good news, prices may rise; On the contrary, when people lose confidence in the market, even without negative factors, prices will fall, and option A is correct. When the market is in a bull market, some insignificant good news will stimulate the optimism of speculators and cause prices to rise; When the market is in a bear market, there is often no good news to reverse the trend of weak prices. Option b is correct. In futures trading, the psychological changes of speculators are often intertwined with futures speculation factors, resulting in a comprehensive effect. Option c is correct. The purpose of speculators is to profit from the fluctuation of futures prices by buying and selling futures contracts. Speculators' psychology is constantly changing with the change of market price, and this psychological change of speculators will become the reason for other speculators' trading behavior. Therefore, the psychological changes of speculators and speculation have formed a mutually restrictive and interdependent relationship in futures trading, and option D is correct.