GATE Mechanical Engineering (ME) 2015 Shift 1 Solved Paper

In the following sentence, certain parts are underlined and marked P, Q and R. One of the parts may contain certain errors or may not be acceptable in standard written communication. Select the part containing an error. Choose D 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).