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

• A. c = 1 and ¬¨‚à묨¬µ‚àö¬™ < 1
• B. c = 1 and ¬¨‚à묨¬µ‚àö¬™ > 1
• C. c = -1 and ¬¨‚à묨¬µ‚àö¬™ = 0
• D. c = ¬¨‚à묨¬µ‚àö¬™ = 1