Keyword to ad function in Dataweave transformation is fun. Hence option 2 and 4 are invalid. Also parameters needs to be passed exactly in same order as defined in function definition. Hence correct answer is'

fun addKV( object: Object, key: String, value: Any) =

object ++ {(key):(value)}

---

addKV ( {"hello': "world"}, "hola", "mundo" )

MuleSoft Documentation Reference : https://docs.mulesoft.com/mule-runtime/4.3/dataweave-functions

DataWeave FunctionDefinition Syntax

To define a function in DataWeave use the following syntax:

fun myFunction(param1, param2, ...) =

The fun keyword starts the definition of a function.

myFunction is the name you define for the function.

Function namesmust be valid identifiers.

(param1, param2, … , paramn) represents the parameters that your function accepts.

You can specify from zero to any number of parameters, separated by commas (,) and enclosed in parentheses.

The = sign marks the beginning of thecode block to execute when the function is called.

represents the actual code that you define for your function.