Which of the following is not a type signature that corresponds to a valid use of function g? function g(a, f) { return a.map(x => f(f(x))).map(x => x.length); } g(string[], string => string): number[] g(m: string[], f: string[] => number[]): number[] gm: string[][], f: (x: string[]) => string[]): number[] g(m: number[][], f: (x: number[]) => number[]): number[]