The power-law transformation is given as: s = crᵞ, c and ᵞ are positive constants, and r is the gray-level of image before processing and s after processing. Then, for what value of c and ᵞ does power-law transformation becomes identity transformation?

• A. c = 1 and ᵞ < 1
• B. c = 1 and ᵞ > 1
• C. c = -1 and ᵞ = 0
• D. c = ᵞ = 1