If only the arbitration court ____ the dispute.

D
1.if only 加一般现在时或will结构表示“希望”：
If only he comes in time=I hope he will come in time.
2.if only加一般过去时或过去完成时表示“懊悔”：
If only he didn't drive so fast.=We are sorry he drives so fast（他要是不开那么快就好了【他现在开得太快】）.
If only I hadn't said that to her.=I wish I hadn't said that to her或 I'm sorry I said that to her.
3.if only + would结构可以用来表达对现在情况的懊悔,其作用与if only+一般过去式一样.像上面2的第一个例子也可以说：If only he wouldn't drive so fast.

选D。
If only... 表示“愿望”，相当于 I wish，所以需要虚拟语气。
句子意思是：
但愿仲裁法庭会解决那个纠纷。

应该是选D。 这是对将来的虚拟。
但是这不是个完整的句子，应该后面还有一部分，感觉这只是状语从句。