根据下面内容，回答下列各题： Salt，shells or metals are still used as money in out of- he wa

y parts of the world today．Salt may seem rather a strange(19)_______to use as money，(20)_______in countries where the food of the people is mainly vegetable，it is often an(21)_______necessity．Cakesb of salt，stamped to show their(22)_______，were used as money in some countries until recent(23)_______ ，and cakes of salt(24)_______buy goods in Borneo and parts of Africa． Sea shells(25)_______as money at some time(26)_______another over the greater part of the Old world．These were(27)_______mainly from the beaches of the Maldives Islands in the Indian Ocean，and were traded to India and China．In Africa，shells were traded tight acrossthe(28)_______from East to West． Metal，valued by weight，(29)_______ coins in many parts of the world．Iron，in lumps，bars or rings，is still used in many countries(30)_______paper money．It Can either be exchanged(31)_______goods，or made into tools，weapons，or ornaments．The early money of China，apart from shells，was of bronze，(32) _______in flat，round pieces with a hole in the middle，called“cash”．The(33) _______of these are between three thousand and four thousand years old older than the earliest coins of the eastern Mediterranean． Nowadays，coins and notes have replaced nearly all the more picturesque forms of money，and while in one or two of the more remote countries people still hold it for future use on ceremonial occasions such as weddings and funerals，examples of primitive money will soon be found only in museums．

A.object

B.article

C.substance

D.category