$(a)$ List two reasons for the appearance of variations among the progeny formed by sexual reproduction.
$(b)$ $(i)$ Name the part marked '$A$' in the diagram.
$(ii)$ How does '$A$' reach part '$B$'?
$(iii)$ State the importance of the part '$C$'.
$(iv)$ What happens to the part marked '$D$' after fertilisation is over?

(N/A) Two reasons for variations in sexual reproduction are:
$(i)$ Involvement of two different individuals (parents) with different genetic makeups.
$(ii)$ Creation of new combinations of gene variants due to the process of meiosis and recombination during gamete formation.
$(b)$ $(i)$ '$A$' represents the Pollen grain.
$(ii)$ '$A$' reaches part '$B$' (stigma) through the process of pollination,which is facilitated by various agents like wind,water,insects,or animals.
$(iii)$ '$C$' is the Pollen tube. Its importance lies in providing a pathway for the male gametes to travel from the stigma to the ovule for fertilisation.
$(iv)$ '$D$' represents the Ovule. After fertilisation,the ovule develops into a seed.