Question

The number of teeth that grow twice in human life is
A) 4
B) 12
C) 20
D) 28

Answer 1

Hint: The teeth are the hardest substance of the body and are made up of white portion that is known as the enamel and it remains embedded in the soft tissues of the mouth that are known as gums. In humans, teeth are used for eating, chewing, tearing of food materials and it aids in the process of digestion.

Complete answer:
The teeth in humans and most of the mammals are important for the process of consumption as well as digestion of foods. The teeth are hard and are present embedded in sockets of the gum. The part of the teeth that is exposed is the enamel portion which is white in color. The roots of the teeth are lodged into the maxilla or upper jaw and into the mandible or the lower jaw. The roots are covered by the gums.
In humans, two sets of teeth develop and due to this feature, the humans are also known as diphyodont. The first set of teeth are known as primary or milk or deciduous set of teeth. They normally start to appear at about six months of age. The primary teeth are about 20 in numbers.
The eruption of the primary teeth is known as eruption and they are further replaced by the permanent teeth. In the primary set of teeth, there are two types of incisors which are placed centrally and laterals while two types of molars which are first and second molar are found. All the primary teeth are replaced by the adult or permanent teeth. It is the second set of teeth and consists of incisors, canines, premolars and molars.
The second set of teeth are known as the permanent teeth and are 32 in numbers. The permanent teeth are also referred to as adult teeth. The lower and upper jaws each contain about 16 numbers of teeth. Thus, the 20 primary teeth are replaced by the permanent teeth which are formed till the age of 13 years.

Therefore, the correct option is option C.

Note: The teeth in humans consist of four types of teeth which are incisors, canines, premolars and molars. The two sets of teeth in humans are known as primary or milk teeth which are 20 in numbers and permanent or adult teeth which are 32 in numbers. There are about 20 teeth in humans which regrow twice to form the permanent set of teeth.