#Java 8, <s>56</s> 55 bytes

<!-- language-all: lang-java -->

    v->" s\n uns\nun s\nun uns".replaceAll(" |s","known$0")

-1 byte thanks to *@SuperChafouin*.

**Explanation:**

[Try it here.](https://tio.run/##LY7BCsIwEETvfsUQPKRgi/ei4AfYi@BFPcQ0Smq6LU1SEe231y0t7A7MLryZSvUqbVpDVfkatVPe46gsfVeApWC6h9IGxWSBU@gsPaHlubEl@iTn68DL44MKVqMAYYexT/cC/kqIxBoJs7ITWWdax8yDc1Lg58VGvKh503orkjGfYW28O4YtzH4Kq7mTnPMvN6hkKfTxwdRZE0PW8is4kpRpSdG5ZGk3jH8)

    v->                         // Method with empty unused parameter
      " s\n uns\nun s\nun uns"  //  Literal String
       .replaceAll(" |s",       //  Replace all spaces and "s" with:
         "known                 //   Literal "known"
               $0")             //   + the match (the space or "s")
                                // End of method (implicit / single-line return-statement)