The series of major changes in the body structure of a growing organism during its life cycle in order to transform from a young one to an adult is called __________.

Options

A. Fertilization
B. Reproduction
C. Metamorphosis
D. None of them

Explanation

The series of major changes in the body structure of a growing organism during its life cycle, transforming it from a young one to an adult, is called **metamorphosis**.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the term that describes the significant changes in body structure as an organism grows from a juvenile to an adult form.

2. **Identifying the Process**: The process of transformation that occurs in many organisms, such as insects, amphibians, and some other animals, involves distinct stages of development.

3. **Examples of Metamorphosis**: A common example is the life cycle of a butterfly:
- **Egg**: The life cycle begins with an egg.
- **Caterpillar (Larva)**: The egg hatches into a caterpillar, which is the larval stage.
- **Pupa (Chrysalis)**: The caterpillar then forms a pupa, where significant changes occur.
- **Adult Butterfly**: Finally, the adult butterfly emerges from the pupa.

4. **Defining Metamorphosis**: The term "metamorphosis" specifically refers to these changes that occur in the life cycle, leading to the development of an adult organism from a juvenile form.

5. **Conclusion**: Therefore, the answer to the question is that the series of changes is called **metamorphosis**.