付款条件的英文表达 — 国际贸易填空题
题目
某出口公司与西班牙客户成交一批运动水壶，合同金额为 USD 45,000.00，付款条款约定：买方须以电汇（T/T）方式预付合同金额的20%作为定金，其余80%货款采用不可撤销即期信用证（L/C at sight）支付。请补全该付款条款的英文表达：Payment shall be made by T/T for 20% of the contract value as deposit in advance, and the remaining 80% by ____ L/C at sight.