The breeding tool used for commercial hybrid seed production in rice is

Correct option is B

Commercial hybrid rice seed production requires stable male sterility.
Cytoplasmic Genetic Male Sterility (CGMS) system is widely adopted.
It involves A, B and R lines for hybrid development.
CGMS ensures large-scale hybrid seed production without manual emasculation.
Hand pollination is impractical for rice. Thus, CGMS is the most suitable breeding tool.
Therefore, option (b) is correct.