A.selling the contract offered at the higher price and selling the contract offered at the lower price
B.buying the contract offered at the higher price and buying the contract offered at the lower price
C.buying the contract offered at the higher price and selling the contract offered at the lower price
D.以較高的價(jià)格出售合同，以較低的價(jià)格購(gòu)買(mǎi)合同