Final answer:
The original sentence contained a misplaced modifier, implying that the keyboard needed to finish by the deadline instead of Sylvia. Rephrasing the sentence to make Sylvia the subject corrects this issue.
Step-by-step explanation:
The sentence 'To finish by the 3 p.m. deadline, the computer keyboard sang with Sylvia's flying fingers.' contains a misplaced modifier. The modifier 'To finish by the 3 p.m. deadline' suggests that it was the keyboard that needed to finish by the deadline, but the intent is to say that Sylvia needs to finish by the deadline. A clearer way to phrase this would be: 'To finish by the 3 p.m. deadline, Sylvia's fingers flew over the computer keyboard.' This corrects the misplaced modifier by making Sylvia the subject who is acting to meet the deadline.