Question: How many images have "picture" as their attribute class and "bear" as their object class?
SQL: SELECT COUNT(T2.IMG_ID) FROM ATT_CLASSES AS T1 INNER JOIN IMG_OBJ_ATT AS T2 ON T1.ATT_CLASS_ID = T2.ATT_CLASS_ID INNER JOIN IMG_OBJ AS T3 ON T2.IMG_ID = T3.IMG_ID INNER JOIN OBJ_CLASSES AS T4 ON T3.OBJ_CLASS_ID = T4.OBJ_CLASS_ID WHERE T1.ATT_CLASS = 'picture' AND T4.OBJ_CLASS = 'bear'