The thread-like structures in the nucleus are called chromosomes.

Mother's milk.

This period of Changes, i.e adolescence begins around the age of 11 and lasts upto 18 or 19 years.

No, all the parts of the body do not grow at the same rate.

Yes, the other term for adolescence is teenage.

We should avoid taking medicines/drugs unless prescribed by a doctor because
(i) several medicines have adverse side effects and have specific dosage levels which if not followed may harm the body.
(ii) drugs can be addictive too and can ruin our health and happiness.

Yes, it is right because beginning of menstruation, i.e. reproductive life begins at 10-12 years of age is known as menarche and stoppage of menstruation, i.e. females can't reproduce now at 45-50 years of age is known as menopause.

No, in human females, each time during maturation and release of egg, the inner wall of uterus thickens. This thickening of the uterine wall is not permanent.
If the egg gets fertilised, it starts developing and gets embedded in the uterine wall resulting in pregnancy. During pregnancy, no more eggs are released and the thickened lining is discharged only when the baby is born. However, if fertilisation does not occur, the released egg and the thickened lining are shed off resulting in menstruation.

Yes, if people do not have enough iodine in their diet, then they may suffer from goitre. This is because iodine is required by the thyroid gland to secrete thyroxine. The lack of thyroxine causes goitre.
lodised salt is table salt mixed with a minute amount of various salts of element iodine. It is important for the thyroid gland to make thyroxine and to prevent mental retardation and stunted growth in children.

Factors which affect the height of the person are
(i) The height of an individual is more or less similar to that of family members. The height depends on the genes inherited by the parents.
(ii) Height also depends on the food eaten by the person in growing period.
(iii) Hormones, exercise and disease also contributes to height.

In our country, the legal age for marriage is 18 years for girls and 21 years for boys. This is because teenage mothers are not prepared mentally or physically for motherhood. Early marriage and motherhood causes health problems in both mother and the child. It also curtails employment opportunities for the young woman and may cause mental agony as she is not ready to shoulder responsibilities of motherhood.
Also, the boys before that age may not be mentally matured and financially secure enough to take the responsibilities of a family. Thus, one should get married only after a certain set age.

Body changes during adolescence are given below