GATE Electronics and Communications (EC) 2015 Shift 2 Solved Paper

In the following sentence, certain parts are marked in bold and marked P, Q and R. One of the parts may contain certain error or may not be acceptable is standard written communication. Select the part containing an error. Choose 4 as your answer if there is no error.
The student corrected all the errors (P) that the instructor marked (Q) on the answer book. (R)