Diaoyu Island(岛) lies the northeast of China and Taiwan Island is the southeast of China.

问题补充：

Diaoyu Island(岛) lies the northeast of China and Taiwan Island is the southeast of China. They are both parts of China.

A.in; onB. on; inC. in; in

答案：

解析：句意：钓鱼岛位于中国的东北方向，台湾在中国的东南方，它们都是中国的一部分。lie in 强调位于范围之内，故选C