School is back in session, and a normal part of it is tests which the teacher must check at home. Usually any mistakes you make are underlined with a red pencil, and the teacher adds his or her comments. For the sake of variety, today we are turning the tables and letting you play the role of the teacher.
There are mistakes in each of the following sentences. Your job is to find them, explain why they are wrong and indicate the correct form. The answers can be found in the printed version of "The World of English" magazine.