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 Function Definition 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 names must 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 the code block to execute when the function is called.
represents the actual code that you define for your function.