Which of the following statements is true about formal parameters?

Formal parameters are specifically designed to carry information into methods. When a method is defined, the formal parameters are listed in the method's signature and act as placeholders for the values (actual parameters) that will be passed to the method when it is invoked. This mechanism allows methods to operate on information and maintain flexibility, as the same method can be reused with different inputs.

The other options present misunderstandings regarding formal parameters. For example, they can be defined only within the method signature and not outside of it, and there is no restriction that all formal parameters must be of the same data type as methods can have parameters of different types. Furthermore, formal parameters themselves can be reused across different method definitions or calls, depending on the programming context.