. . . . . . . . function is used to format numbers.

The correct answer is: A. toString

The toString() function is used to convert a value to a string. It can be used to format numbers, dates, and other values.

The toNumber() function is used to convert a string to a number. It can be used to parse numbers from user input or from other sources.

The toFormat() function is not a standard JavaScript function. It may be defined by a library or framework.

The toSpecify() function is not a standard JavaScript function. It may be defined by a library or framework.

Here is an example of how to use the toString() function to format a number:

javascript
var number = 123456789;
var string = number.toString();
// string is "123456789"

Here is an example of how to use the toNumber() function to parse a string:

javascript
var string = "123456789";
var number = Number(string);
// number is 123456789