A tadpole with surgically removed thyroid gland can be made to metamorphose if

Options

A. Given an injection of TSH
B. Given an injection of oxytocin
C. Given an injection of thyroxine
D. Fed on dried thyroid gland.

Answer

### Step-by-Step Solution:

1. **Understanding the Role of Thyroid Gland**:
- The thyroid gland produces hormones, particularly thyroxin, which are crucial for the growth and metamorphosis of amphibians, such as frogs.

2. **Identifying the Problem**:
- In this scenario, a tadpole has had its thyroid gland surgically removed. Without the thyroid gland, the tadpole cannot produce thyroxin, which is essential for its metamorphosis into an adult frog.

3. **Considering the Options**:
- **Option A: Given an injection of TCH**: TCH (Thyroid Stimulating Hormone) stimulates the thyroid gland but does not induce metamorphosis directly since the gland is removed.
- **Option B: Given an injection of oxytocin**: Oxytocin is unrelated to amphibian metamorphosis; it primarily affects reproductive processes in mammals.
- **Option C: Given an injection of thyroxin**: This option directly provides the hormone that the tadpole lacks due to the removal of the thyroid gland.
- **Option D: Fed on dried thyroid gland**: This option is ineffective because simply consuming dried thyroid tissue does not provide the necessary hormonal action required for metamorphosis.

4. **Conclusion**:
- The correct answer is **Option C: given an injection of thyroxin**. This hormone is essential for the metamorphosis of the tadpole into an adult frog.