问题详情

What was the important event in December 19797
A．China switched from state planning and isolationism to reform. and the open-door policy.
B．China applied to join GATT.
C．China began to negotiate with the US party in order to make the entry for GATT.
D．China decided to join the world" s principal trading body.请帮忙给出正确答案和分析，谢谢！