The default parameter passing mechanism isQuestion 3Answera.Call by value resultb.None of thesec.Call by valuesd.Call by reference

The default parameter passing mechanism is typically "Call by value".

Here's a step-by-step explanation:

1. In most programming languages, the default parameter passing mechanism is "Call by value". This means that when a function is called, the values of the actual parameters are copied into the function's formal parameters.

2. During the execution of the function, the formal parameters act as new variables and any changes made to them do not affect the actual parameters.

3. For example, if you have a function that increments a number and you pass a variable with a value of 5 to this function, the function will increment the copy of the variable, not the original one. So, after the function is executed, the original variable will still have a value of 5.

4. The other parameter passing mechanisms - "Call by reference" and "Call by value result" - are not typically the default. "Call by reference" means that a reference to the actual parameter is passed to the function, so any changes made to the formal parameter will affect the actual parameter. "Call by value result" is a combination of the two - the function gets a copy of the actual parameter but the actual parameter is updated with the value of the formal parameter when the function returns.

5. However, the default mechanism can vary depending on the programming language. For example, in Java, the default is "Call by value" for primitive types and "Call by reference" for objects.