介宾短语指代 eg082219：Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of the Greater Antilles islands.此句错误。it指代不清楚，代词难以指到介词的宾语。只有在非常明确的情况下，it才可以指代介宾短语里的词。如og11 86： Since 1986, when the Department of Labor began to allow fees of investment officers to be based on the performance of the funds they manage, several corporations have begun paying their investment advisers a small basic fee, with a contract promising higher fees if the managers perform well.【此句正确】