Ma'am,

    For this question - "Cross pollination in the technique of hybridisation is prevented by ______________."

Should we write the answer as _bagging_ or emasculation?

Emasculation will be the appropriate answer because emasculation prevents self pollination.The purpose of emasculation is to prevent self-fertilization in the flowers of female parent. But we can test the efficeicency of the emasculation technique by bagging the emasculated flowers without pollination.