In JavaScript, which of the following best describes what functions are capable of doing in terms of parameters and return values?

Introduction / Context:
JavaScript functions are fundamental building blocks used to structure programs, reuse code, and implement logic. A basic concept that learners must understand is how functions interact with data: they can receive input through parameters and can provide results through return values. This question asks which statement correctly describes these capabilities in JavaScript.

Given Data / Assumptions:

• We are working with standard JavaScript running in a browser or Node.js.
• Functions are declared using function syntax or expressions.
• Parameters allow functions to receive input values.
• The return statement allows a function to send a value back to its caller.

Concept / Approach:
In JavaScript, you can define a function with zero or more parameters. When the function is called, arguments are passed for these parameters. Inside the function, you can use the return statement to send back a value to the caller. If no return statement is executed, the function returns undefined by default. Thus, functions are flexible: they can accept parameters, they can return values, and they can also be used purely for side effects when no return value is needed.

Step-by-Step Solution:
Step 1: Consider whether a function can accept parameters. In JavaScript, function definitions list parameters in parentheses, so the language clearly supports this. Step 2: Consider whether a function can return a value. The return keyword is used to send a value back to the caller, so this is also supported. Step 3: Therefore, a correct description must state that functions can both accept parameters and return a value. Step 4: Option c explicitly says that functions can accept parameters and can also return a value, matching JavaScript behavior. Step 5: Options a, b, d, and e each deny part or all of this capability, so they are incorrect.

Verification / Alternative check:
A simple example confirms this: function add(a, b) { return a + b; } defines a function that accepts two parameters and returns their sum. Calling add(2, 3) returns 5. This demonstrates that both parameters and return values are supported. Many standard JavaScript APIs also expect callback functions that receive arguments and return values, reinforcing the correctness of option c.

Why Other Options Are Wrong:
Option a incorrectly states that functions can never return a value, which is contradicted by the return keyword. Option b incorrectly claims that functions cannot accept parameters, which is not true. Option d says that functions can neither accept parameters nor return values, which would make them useless for most programming tasks. Option e wrongly describes functions as comments, which is factually wrong because comments are ignored by the interpreter.

Common Pitfalls:
Some beginners forget to include a return statement in functions that are supposed to compute a result, leading to undefined being returned. Others misunderstand parameter passing and expect changes to primitive arguments to affect the original variables outside the function. However, the core capability remains: functions can take parameters and can return values.

Final Answer:
In JavaScript, functions can accept parameters and can also return a value, which is correctly expressed by option c.