I have a content type that has 3 term reference fields:

- Field A (required), which contains a single tag.
- Field B (required), which contains a single tag.
- Field C (not required), which contains a single tag.

The tags from those 3 fields all related to the same taxonomy.

When creating or updating a node, values are entered for field A and B. I want to have a rule ((using the [Rules](https://www.drupal.org/project/rules) module) with some Rules Action to set a  data value for field C, equal to the concatenation of the value entered for field A and B. But "set a data value" only sets one value. 

What can I do to set multiple values?

Some more screenprints to explain all this:

[![enter image description here][1]][1]

[![enter image description here][2]][2]

[![enter image description here][3]][3]

And here is my current Rule I'm trying to get to work:

    { "rules_juhe_xieru" : {
        "LABEL" : "\u805a\u5408\u5206\u7c7b\u81ea\u52a8\u5199\u5165",
        "PLUGIN" : "reaction rule",
        "OWNER" : "rules",
        "REQUIRES" : [ "rules" ],
        "ON" : { "node_insert--mfpf" : { "bundle" : "mfpf" } },
        "DO" : [
          { "data_set" : { "data" : [ "node:field-juhe-fenlei" ], "value" : [ "node:field-diqu" ] } }
        ]
      }
    }


  [1]: https://i.sstatic.net/jCouZ.png
  [2]: https://i.sstatic.net/hV8LO.png
  [3]: https://i.sstatic.net/XhSgK.png