Self-pollination and cross-pollination both can occur in chasmogamous flower. For details,refer Basics and Basis.

In a 3-celled pollen, there is one vegetative or tube cell and two male gametes. in two-celled pollen, there is one vegetative cell and a generative cell. Here  the generative cell divides in the pollen tube to form two male gametes which are already present in 3-celled pollen. Therefore, there is no need for further division in 3-celled pollen. 

1. In haploid organisms, showing haplontic life cycle, gamete formation involves only mitosis; the diploid zygote formed by the fusion of two haploid gametes, undergoes meiosis (zygotic meiosis).
2. In diploid organisms, showing diplontic or haplodiplontic life cycle, gamete formation involues meiosis (gametic meiosis) and haploid gametes are formedl; the diploid zygote undergoes mitosis to form diploid individuals.

i) The part A is seed and B are pericarps.
ii) The part of the flower which develops into seed and fruit is ovule and ovary, respectively
iii) The seeds germinate to produce new plants while pericarp is protective in function.It protects the young seed.

(a) The ponds were covered with a water weed which is commonly called as water hyacinth (Eichhornia crassipes).
(b) It propagates vegetatively by offsets at an alarming rate thereby spreading all over the water, totally covering it within a short period. Its thick cover over the water body prevents light entering the water and reduces the oxygen level of water. This results into the death of fishes and aquatic life in greatly disturbed.