Please help me with this Python question. Thank you!

Select all the statements that are correct. Select one or more: O a. First class functions means that functions can call themselves. b. First class functions means that references to functions can be stored in data structures. C. First class functions means that a function must be defined first before it can be called. d. First class functions means that functions can be used as parameters. e. First class functions means that they have parameters and return a value. of. First class functions means that functions can be used as return values