The reproductive period is marked by characteristic events repeated almost every month in physiologically normal woman (28 days with minor variation) in the form of a menstrual flow
The menstrual cycle consists of 4 phases:
(i) Menstrual or Destructive phase 
(ii) Follicular or Proliferative Phase
(iii) Ovulatory Phase
(iv) Luteal or Secretory Phase 

(i) The main part of the ovule is the nucellus which is enclosed by two integuments leaving an opening called as micropyle.
(ii) The ovule is attached to the ovary wall by a stalk known as funiculus.
(iii) Chalaza is the basal part.
(iv) The embryo sac contains seven cells and eight nuclei located within the nucellus.
(v) Three cells at the micropylar end form the egg apparatus and the three cells at the chalaza end are the antipodal cells.
(vi) The remaining two nuclei are called polar nuclei found in the centre.
(vii) In the egg apparatus one is the egg cell (female gamete) and the remaining two cells are the synergids.

a) The first menstruation is called menarche. It occurs at the age of 11 to 13 years.
b) Napkin hygiene measures are:
(i) The sanitary pad and tampons should be wrapped properly and discarded because they can spread infections.
(ii) Sanitary pad or tampon should not be flushed down the toilet.
(iii) Napkin incinerators are to be used properly for disposal of used napkins.
c) Rahini's objection is correct.
(i) The advertisement gives some knowledge about the napkin.
(ii) How to use the napkin and what is the purpose of it.
(iii) The advertisement is answers some more questions.
(iv) It create the awareness among the females. So the object are correct.

(i) Before puberty and during development, the secretion of estrogen and progesterone are not secreted.
(ii) So it does not form ovary.
(iii) So menstrual does not take place before puberty and during pregnancy.

(i) Vegetative cell degenerates and the generative cell divides to form two sperms (or male gametes)
(ii) Tip of pollen tube bursts and the two sperms enter the embryo sac.
(iii) One sperm fuses with the egg (syngamy) and forms a diploid zygote.
(iv) The other sperm fuses with the secondary nucleus (Triple fusion) to form the primary endosperm nucleus which is triploid in nature.
(v) Since two types of fusion syngamy and triple fusion take place in an embryo sac the process is termed as double fertilization.
(vi) After triple fusion, primary endosperm nucleus develops into an endosperm.
(v) Endosperm provides food to the developing embryo.
(vi) The purpose of carrying two gametes is one is to form zygote another is to form endosperm to provide food to the developing embryo.