(a) The protruding part of the throat, as seen in the neck of the adult is called Adam’s apple. At the time of puberty, this voice box grows in size and visible from outside in boys. This makes the voice of boys hoarse.

(b) These are features features that help in distinguishing the male and the female body from each other. They are physical or behavioural characteristics that appear in humans at the time of puberty.

Secondary sexual characters in boys:

1) Appearance of moustache and beard.

2) Appearance of chest hair.

3) Growth of hair in genital area and other body.

Secondary sexual character in girls:

1) Increase in breast size.

2) The appearance of facial hair.

3) Growth of hair in genital area and other body parts.

(c) Sex of a unborn baby depends upon the pair of sex chromosomes that are present in the cells of the baby.

The two sex chromosomes are X and Y.

The unfertilised egg always has one X chromosome.

But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome.

If both the chromosmes are X then the baby is Female child.

If one of the chromosomes are X and the other is Y then the baby is Male child.