Appropriate techniques have been developed for large scale cell culture using bioreactors for producing :

Options

A. A. foreign gene product
B. B. vaccines
C. C. hormones
D. D. all of these

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the techniques developed for large-scale cell culture using bioreactors and what products can be produced through these techniques.

2. **Identifying the Need for Large-Scale Production**: Small volume cultures are insufficient for yielding significant quantities of products. Therefore, large-scale production is necessary.

3. **Introduction to Bioreactors**: Bioreactors are specialized vessels designed to facilitate the conversion of raw materials into specific products. They provide controlled conditions for cell growth and product formation.

4. **Types of Products Produced**:
- **Foreign Gene Products**: These are proteins or other products that are produced from genetically modified organisms.
- **Vaccines**: Bioreactors can be used to culture cells that produce vaccines, which are essential for immunization.
- **Hormones**: Many hormones can be produced using cell cultures in bioreactors, which are crucial for various physiological functions.

5. **Conclusion**: Since bioreactors can be utilized to produce foreign gene products, vaccines, and hormones, the correct answer is that they can produce all of these products.

6. **Final Answer**: The appropriate techniques have been developed for large-scale cell culture using bioreactors for producing **d) all of these**.