Explanation:

In humans, milk teeth, also known as deciduous teeth or primary teeth, are the first set of teeth that erupt in the mouth. These teeth start to appear in children typically around the age of 6 months and continue to develop until the age of about 2-3 years. Milk teeth are eventually replaced by permanent teeth as the child grows.

Milk Teeth Count:
The correct answer is option 'B' - 20 milk teeth in a child. Here's a breakdown of the milk teeth count:

Incisors:
- There are 8 incisors in total, 4 in the upper jaw and 4 in the lower jaw.
- Incisors are the front teeth that are used for biting and cutting food.

Canines:
- There are 4 canines in total, 2 in the upper jaw and 2 in the lower jaw.
- Canines, also known as cuspids, are the pointed teeth located on either side of the incisors. They are used for tearing and grasping food.

First Molars:
- There are 8 first molars in total, 4 in the upper jaw and 4 in the lower jaw.
- First molars have a flat surface with multiple cusps and are used for grinding and chewing food.

Second Molars:
- There are 8 second molars in total, 4 in the upper jaw and 4 in the lower jaw.
- Second molars are located behind the first molars and also have a flat surface with multiple cusps for grinding and chewing food.

Total:
- 8 incisors + 4 canines + 8 first molars + 8 second molars = 28 milk teeth in total.

Since each milk tooth has a pair (one in the upper jaw and one in the lower jaw), the total count is 20 milk teeth in a child.

It's important to note that the milk teeth start to fall out naturally around the age of 6-7 years, and they are gradually replaced by permanent teeth. The permanent teeth count in adults is 32, including incisors, canines, premolars, and molars.