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

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