When fertilization take place in plants ?

What is the major disadvantage of external Fertilization ?

Which is correct sentence ?

Which of the following statements is incorrect ?
$(i)$ Bamboo species flower only once in their life time, generally after $50-100$ years and produce large number of fruits and die.
$(ii)$ In animals, the juvenile phase is followed by morphological and physiological changes prior to active reproductive behaviour.
$(iii)$ The reproductive phase is of same duration in all organisms.
$(iv)$ Juvenile phase is the period of growth between the birth of an individual till it reaches reproductive maturity.

Which type of propagation is better for the plant