Genetic engineering has been successfully used for producing:

Options

A. transgenic mice for testing safety of polio vaccine before use in humans
B. transgenic models for studying new treatments for certain cardiac diseases
C. transgenic cow-Rosie which produces high fat milk for making ghee
D. animals like bulls for farm work as they have super power

Answer

**Step-by-Step Solution:**

1. **Understanding Genetic Engineering**: Genetic engineering refers to the direct manipulation of an organism's genes using biotechnology. It has various applications, including the production of transgenic organisms.

2. **Analyzing the Options**:
- **Option A**: Transgenic mice for testing safety of polio vaccine before using in humans.
- **Option B**: Transgenic models for studying new treatment for certain cardiac diseases.
- **Option C**: Transgenic cow Rosie which produces high-fat milk for making ghee.
- **Option D**: Animals like bulls for farm work as they have super power.

3. **Evaluating Option A**:
- The polio vaccine is developed using attenuated (weakened) viruses. Before mass production, it is crucial to test the vaccine for safety. Transgenic mice have been used successfully for this purpose. Thus, this option is correct.

4. **Evaluating Option B**:
- While transgenic models can be used in research, there is no significant evidence that they have been successfully used specifically for studying new treatments for cardiac diseases. Therefore, this option is incorrect.

5. **Evaluating Option C**:
- The production of high-fat milk from cows like Rosie typically involves selective breeding rather than genetic engineering. Hence, this option is incorrect.

6. **Evaluating Option D**:
- Similar to option C, improving farm animals like bulls for work purposes is achieved through breeding practices rather than genetic engineering. Thus, this option is also incorrect.

7. **Conclusion**: Based on the evaluations, the only correct application of genetic engineering among the provided options is the use of transgenic mice for testing the safety of the polio vaccine before it is used in humans.

**Final Answer**: Transgenic mice for testing safety of polio vaccine before using in humans.

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