将8克SO₃加入X克水中，所形成的溶液里，SO₄^2-和水分子个数比为1：5，则X等于

A．9克

B．10.8克

C．12.4克

D．15.6克

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)