a, an (indefinite articles) and the (definite article) are the article in an English language.
My neighbour is (i) <u>an</u> university professor. He is (ii) <u>a</u> good man. He teaches some poor children of (iii) <u>a</u> nearby slum area for (iv) <u>an</u> hour every evening for free. (v) <u>The</u> children are very fond of him.
The returned papers will show the correct answers because they from students who did not skipped the class.In most cases that will help with the validity of the results if the professors wants to see the deviations with the marks obtained from both parties.