How many images have "vegetable" and "fruits" as their object classes?
images refer to IMG_ID; "vegetables" and "fruits" as object classes refer to OBJ_CLASS = 'vegetables' and OBJ_CLASS = 'fruits';
SELECT COUNT(T1.IMG_ID) FROM IMG_OBJ AS T1 INNER JOIN OBJ_CLASSES AS T2 ON T1.OBJ_CLASS_ID = T2.OBJ_CLASS_ID WHERE T2.OBJ_CLASS = 'vegetables' OR T2.OBJ_CLASS = 'fruits'