The study you have been making -------- the ancient Chinese

选择of
“你一直在进行的对于中国古代人物的研究是一份有意义的工作.”
你把"you have been making"去掉,不影响句子的意思,这是个插入语.
就变成了"The study___the ancient Chinese characters is an instructive job."
这样应该就简单多了吧.
"The study_of__the ancient Chinese characters is an instructive job."
of经常表示“什么_的_什么”
希望你会明白咯~