In the test, and every time he wants to let you correct the error, as individuals, which makes students understand and learn the error of their own points.
To do the test, and works every time you want to correct errors individually, which will give students a greater understanding and knowledge of the errors of their own.
In the test and the works every time you want to fix the error to the individual, which makes the students have more understanding and know the mistake of their own.