If there is NO error in a line, write down "No Error" in the space provided. You put a tick (√) in the actual exam, but putting a tick here will render your answer wrong when checked against the answer key.
If the line is incorrect, write the correct word in the space provided (this is when you also have to circle the incorrect word in the actual exam, but not here).
The correct word you provide must not change the original meaning of the sentence.
The first sentence contains no errors.