The correct option is C Length of juvenile/ Vegetative phase
Bamboo (Bambusa) produces flowers only after 50-100 years, produce large number of fruits once in their lifetime and die. Another such example is the Neelakuranji (Strobilanthus kunthiana) which flowers synchronously after every 12 years, set seeds and die. And hence they are both monocarpic and not polycarpic. And only thing that they differ in is the juvenile phase which is longer for the Bamboo and shorter comparitively for strobilanthus.