Concept:Convert the times to a 24-hour format and subtract the start time from the end time.Explanation:Work start time: 7:55 a.m. is 7 hours 55 minutes.Work end time: 4:15 p.m. in 24-hour time is 16:15, which is 16 hours 15 minutes.Subtract the start from the end: 16 hours 15 minutes −7 hours 55 minutes.Hour difference: 16−7=9 hours.Minute difference: 15−55=−40 minutes.Since the minutes are negative, borrow 1 hour from 9 hours.1 hour =60 minutes, so 9 hours becomes 8 hours and 60 minutes.Total time =8 hours +(60−40) minutes =8 hours 20 minutes.Thus, Jane was at work for 8 hours 20 minutes, which is option C.Answer:8 hr 20 min, i.e., Option C.