The engineers and the workers have overe a lot of difficulty some new products．A.they had developedB.to have developedC.they had developingD.having developed
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C解析a lot of difficulty they had in developing some new products意思是“他们在开发新产品时所碰到的许多困难”。在这个词组中的they had是定语从句，修饰difficulty，这个词组正常的语序应该是they had a lot of difficulty in developing some new
products，而在这个词组中介词in是可以被省略的。