答案A少个had吧,如果是这样,我帮你分析这个题目：主语the scientist and technicians 谓语overcame 宾语a lot of difficulty they had developing the personal computer.为省略关系代词that的定语从句修饰a lot of difficulty .that指代difficulty,转化为单句：they had a lot of difficulty （in）developing the personal computer.
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