A function block is enclosed with?

In JavaScript, a function block is enclosed with curly braces, which are represented by the {} symbols. This is essential because curly braces define the boundaries of a block of code that belongs to a specific function. When you define a function, you use the function keyword followed by the function name and parentheses for parameters; then, you open a curly brace to start the function body, which contains the code that will execute when the function is called.

The use of curly braces helps to group statements together, allowing the function to control the scope of variables declared within it and maintain clean, organized code. This makes it clear where the function begins and ends, which is crucial for the readability and maintainability of code.

Other types of brackets serve different purposes in JavaScript; for instance, parentheses () are used for enclosing function parameters and controlling the order of operations in expressions, while square brackets [] are used for array definitions and indexing. The combination of parentheses and square brackets as seen in the last option does not correspond to any conventional syntax for defining function blocks. Thus, curly braces are the correct choice for enclosing the body of a function.