下列几种付款方式中，对出口方来说最不安全的是（）

• A、100%T/T in advance
• B、30%T/T in advance，and the balance to be paid by L/C at sight
• C、10%T/T in advance，and the balance to be paid by L/C at 90 days’ sight
• D、40%T/T in advance，and the balance to be paid by T/T after receipt of goods