The correct option is B. between conception and parturition. Detailed Explanation:

1. Definition of Gestation Period:
2. The gestation period refers to the duration of time from the moment of conception (when the sperm fertilizes the egg) until the birth of the offspring (parturition). This period varies significantly among different species of animals. For example, humans have a gestation period of about 9 months, while other animals like elephants can have a gestation period of up to 22 months.
3. Understanding Conception and Parturition:
4. Conception: This is the initial stage of reproduction where the sperm successfully fertilizes the ovum (egg). This marks the beginning of the gestation period.
5. Parturition: This is the process of giving birth, which marks the end of the gestation period.
6. Why Option B is Correct:
7. Option B accurately captures the entire duration of the gestation period, which is the time frame from conception (fertilization) to parturition (birth). This definition encompasses all the developmental stages that the embryo undergoes during pregnancy.

Why the Other Options are Incorrect:

• Option A: of fusion of the sperm and the egg:
• This option only describes the moment of fertilization, which is just the starting point of the gestation period. It does not account for the entire duration until birth, making it an incomplete definition.
• Option C: of release of ovum from the ovary:
• This option refers to ovulation, which is the process where an ovum is released from the ovary. While this is a crucial part of reproduction, it does not define the gestation period, as it does not include the fertilization or the subsequent development of the embryo.
• Option D: of the birth of the young animal:
• This option only describes the endpoint of the gestation period (parturition) and does not include the time leading up to it. Therefore, it fails to provide a complete understanding of what the gestation period entails.

Summary of Key Points:

• The gestation period is the time from conception (fertilization) to parturition (birth).
• It includes all developmental stages of the embryo and fetus.
• Understanding the full scope of gestation is crucial for animal husbandry and reproductive management in agriculture.
• Recognizing the differences between conception, ovulation, and parturition is essential for clarity in reproductive biology.

By grasping these concepts, students can better understand reproductive processes in agricultural science and their implications for animal breeding and management.