付款条件的英文表达 — 国际贸易选择题

某出口公司与加拿大客户就一批灯具达成交易，约定：买方须在发票日后45天内以不可撤销的即期信用证付款。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 L/C within 45 days after the invoice date. B. Payment shall be made by an irrevocable L/C at 45 days after sight. C. Payment shall be made by T/T within 45 days after the invoice date. D. Payment shall be made by a confirmed sight L/C at 45 days after the invoice date.