A protion of destarched leaf of a potted plant was covered with a black strip of paper. The plant was then exposed to sunlight for six hours and then tested for starch. It was observed that:
A. both covered and uncovered parts of leaf turned blue-black
B. both covered and uncovered parts of leaf turned yellowish-brown
C. only the uncovered part of leaf turned blue-black
D. only the covered part of leaf turned blue-black
