Step 1: Understand the question context
The question is asking about the necessary characteristics that an asset must have to be considered as foreign exchange (外汇).

Step

To be considered as foreign exchange, an asset typically needs to have certain qualities that make it a viable and acceptable form of exchange internationally.

Step

The three key characteristics often associated with foreign exchange assets are:
1、可支付性 (Payment capability or acceptability): The asset must be widely accepted as a means of payment.
2、可兑换性 (Convertibility): The asset should be easily convertible into other currencies or assets.
3、可偿性 (Repatriability or transferability): The asset must be capable of being transferred or repatriated.

The best answer is 可支付性、可兑换性、可偿性.