Answer: (ii) proper diet is needed for the rapid growth taking place in their body.
Answer: (i) menstruation starts.
Answer: (ii) chapatti, dal, vegetables.
Appearance of moustache and beard.
Appearance of chest hair.
Growth of hair in genital area and other parts of the body.
Increase in breast size and darkening of the skin of nipples present at the tip of the breasts.
Growth of hair in genital area and other body parts.
(c) Sex of an 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 unfertilized 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 chromosomes are X then the baby is girl. If one of the chromosomes are X and the other is Y then the baby is boy.