付款条件的英文表达 — 国际贸易选择题

某出口公司与澳大利亚客户成交一批陶瓷餐具，合同约定买方须开立以卖方为受益人的不可撤销即期信用证付款。下列付款条款的英文表述正确的一项是（　） A. Payment shall be made by an irrevocable sight Letter of Credit in favor of the seller. B. Payment shall be made by a revocable usance Letter of Credit in favor of the buyer. C. Payment shall be made by T/T within 30 days after shipment. D. Payment shall be made by an irrevocable sight Letter of Credit in favor of the buyer.