1. Could you tell me which kind of payment terms you'll choose?
能否告知你們將采用哪種付款方式？
還能這樣說：
Could you tell me how you will pay for it?
Could you tell me what your payment terms are?
應用解析：
on easy terms 以分期付款的方式，以優厚的條件

2. This is the normal terms of payment in international business.
這是國際貿易中慣用的付款方式。
還能這樣說：
People usually use this kind of payment in international trade.
This payment is often seen in international business.
應用解析：
be normal to 垂直于，成直角；
off normal 越界的，不正常

3. We will pay in installments.
我們將分期付款。
還能這樣說：
We will pay on easy terms.
We can buy it on an installment basis.

4. They demand prompt payment.
他們要求立即付款。
還能這樣說：
They demand to pay immediately.
They require that we should pay at once.
應用解析：
be prompt to obey commands 立即服從命令；
prompt sb.'s thought 激起某人的思想；
prompt sale 期貨交易