a) Teratogens
b) The pregnant woman must consult a doctor before taking any medicine
c) Amniotic fluid.

a) Inner cell mass. It forms the tissues of future embryo
b) Morula
c) In the inner cell mass.
d) The pole of the blastocyst that contains the inner cell mass

Reason: fertilisation can only occur if the ovum and sperms are carried simultaneously.

In the absence of fertilization, corpus luteum degenerates which causes disintegration of endometrium leading to menstrual cycle.

Blastula or Blastocyst (32-celled stage).

Chorionic villi appear just after implantation, They appear as fìnger-like projections on the trophoblast and become interdigitated with the surrounding uterine tissues and forms the placenta

The secretion of the acrosome help the sperm enter into the cytoplasm of ovum through zona pellucida and the plasma membrane, this induces the completion of second meiotic division of the secondary oocyte, forming second polar body and a haploid ovum, soon the haploid nucleusof the sperm and that of the ovum fuse tdgether to form a diploid zygote.

Human female reproductive system consists of:
1.The primary sex organ i.e. a pair of ovaries.
2.The secondary sex organs, i.e. the duct system consisting of a pair of fallopirtubes, a uterus, cervix, and vagina.
3.The external genitalia and
4. Mammary glands

(i) 'a'  is zona pellucida.
The changes that occur in it when a sperm comes in contact with it, block the entry of other sperms.
(ii) Ampullary - isthmic junction of fallopian tube.

Follicular phase.
The primary follicles in the ovary grow and become a fully mature Graafian follicle.
The endometrium of the uterus is regenerated by proliferation of the cells.
These changes are due to an increased level of pituitary hormones,FSH and LH and ovarian hormone,estrogen.
FSH controls the follicular phasa; it stimulates the growth of follicles and secretion of estrogen by the follicular cells.
Both FSH and LH reach their peak level in the middle of the cycle.

1.Hymen is the membrane that partially covers the vaginal opening.
2.The hymen gets torn during the first coitus.
3. But it can also be torn by active participation in sports like horse-riding,cycling,or by a sudden fall or jolt and insertion of vaginal tampon;so its presence or absence cannot indicate virginity.