CATDOLL : CATDOLL: In order to solve the problem that the meat quality of diploid common oysters decreases due to spawning in summer, people have cultivated triploid oysters.

A. Inhibiting the first cleavage results in chromosome doubling, and the resulting individual is tetraploid. A is wrong.

B. The sperm with the nucleus destroyed by gamma rays stimulates the egg cell to form a new individual which is haploid. B is wrong.

C. The polar body contains one chromosome set, the fertilized egg contains two chromosome sets, and the fertilized egg with polar bodies contains three chromosome sets. The developed individual is triploid, so C is correct.

D. The Xiangzhouchi individual obtained by transplantation method is diploid, so D is wrong.

Therefore, the answer is: C.