Determine all the singular points of the given differential equation. (?- 3t - 28) x" + (t + 4)x' - (t- 7)x = 0 Select the correct choice below and, if necessary, fill in the answer box to complete...

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Extracted text: Determine all the singular points of the given differential equation. (?- 3t - 28) x" + (t + 4)x' - (t- 7)x = 0 Select the correct choice below and, if necessary, fill in the answer box to complete your choice. O A. The singular points are all t2 and t= (Use a comma to separate answers as needed.) O B. The singular points are all ts and t= (Use a comma to separate answers as needed.) O C. The singular points are all ts O D. The singular point(s) is/are t= (Use a comma to separate answers as needed.) O E. The singular points are all t2 O F. There are no singular points.