GATE EC 2015 Set 2 Q6 — General Aptitude

In the following sentence certain parts are underlined and marked P,Q and R. One of the parts may contain certain error 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.

$\text{The student corrected } \underset{P}{\underline{\text{all the errors}}} \text{ that } \underset{Q}{\underline{\text{the instructor marked}}} \text{ on the } \underset{R}{\underline{\text{answer book}}}.$