In this activity, students review key grammar structures by identifying and correcting mistakes in short sentences. The sentences include a range of common learner errors from A1 to B2 levels, allowing students to activate prior knowledge, notice patterns, and self-evaluate. Students read each sentence, decide whether it is correct or incorrect, rewrite it accurately, and assign a grade. This warm-up encourages careful reading, language awareness, and confidence before moving into the main lesson. It can be done individually, in pairs, or as a whole-class discussion.