下列反应完成后没有沉淀的是(    )

A．BaCl₂溶液与Na₂CO₃溶液加足量稀盐酸

B．Ba(OH)₂溶液与KNO₃溶液加足量稀硫酸

C．AgNO₃溶液与NaCO₃溶液加足量稀盐酸

D．Ca(OH)₂溶液与FeCl₃溶液加足量稀HNO₃

In relation to the United Nations Convention on Contracts for the International Sale of Goods, explain how the following can bring an offer to an end:

(a) withdrawal; (3 marks)