Please list the classes of all the object samples in image no.1.
classes of all the object samples refers to OBJ_CLASS; image no.1 refers to IMG_ID = 1
SELECT T1.OBJ_CLASS FROM OBJ_CLASSES AS T1 INNER JOIN IMG_OBJ AS T2 ON T1.OBJ_CLASS_ID = T2.OBJ_CLASS_ID WHERE T2.IMG_ID = 1 GROUP BY T1.OBJ_CLASS