How many teeth appear twice during the life span of an individual?

Options

A. 16
B. 32
C. 22
D. 20

Explanation

To determine how many teeth appear twice during the lifespan of an individual, we can follow these steps:

### Step 1: Understand the Types of Teeth
- Humans have two sets of teeth during their lifetime: primary (or milk) teeth and permanent teeth.

### Step 2: Identify the Number of Primary Teeth
- The primary teeth, also known as milk teeth, consist of a total of 20 teeth. These usually emerge in early childhood.

### Step 3: Recognize the Replacement of Primary Teeth
- As a child grows, these primary teeth are gradually replaced by permanent teeth. This transition occurs from childhood into adolescence.

### Step 4: Count the Teeth that Appear Twice
- Since the primary teeth (20 in total) are replaced by permanent teeth, these 20 teeth are the ones that appear twice in an individual's lifetime.

### Step 5: Conclusion
- Therefore, the total number of teeth that appear twice during the lifespan of an individual is 20.

### Final Answer
- The answer is **20 teeth**.

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