storyteller: long long ago, there was a seller, he took a spear and a shield to the market, and began to sell them. seller: come on, come on, everyone! come here and have a look, i have the best spear and shield. costmer: well, they are not bad.seller: no bad? they are the best. have you seen my spear? it’s the best in the world , my spear could stab through any shields. costmer 2: oh, really? what about your shield. seller: of course it’s the best, too. it can stop any spears in the world.wise fellow：then…… ,what if your spear fights against your shield? seller: sorry! i forget my own shield?