This is an all-class mixer activity for reviewing definite articles, formation of plural nouns and school supplies. Print on cardstock and cut into cards. Students find a partner. Partner A asks his question (Give the singular of die Lehrer); B responds (der Lehrer). B asks his question (Give the plural of das Buch) and A responds (die Bücher). Students exchange cards and then move on to find new partners. Perfect review activity for right before a test.