付款条件的英文表达 — 国际贸易选择题

某外贸公司同意以即期信用证（L/C at sight）方式收款，但在给客户的确认函中需准确表达付款条款。以下哪项英文表述最准确、最符合国际贸易函电惯例？ A. Payment shall be made by L/C to arrive at our end 30 days before shipment. B. Payment is to be made by irrevocable L/C at sight, to reach us 30 days before shipment. C. Payment will be paid by T/T after you receive the goods. D. Payment should be opened by D/P at sight within 15 days after shipment.