Stirred-tank bioreactors have advantages over shake flasks because they

Options

A. a) provide high temperature and pH
B. b) provide better aeration and mixing properties
C. c) do not allow the entry of `CO_(2)`
D. d) are easy to operate

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the advantages of stirred-tank bioreactors compared to shake flasks. We need to identify the key benefits that stirred-tank bioreactors provide.

2. **Identifying the Options**: The options given are:
- a. provide high temperature and pH
- b. provide better aeration and mixing properties
- c. do not allow the entry of CO2
- d. are easy to operate

3. **Analyzing Each Option**:
- **Option a**: While stirred-tank bioreactors can maintain specific temperature and pH, this is not their primary advantage over shake flasks.
- **Option b**: Stirred-tank bioreactors are designed to ensure better aeration and mixing due to their design and stirring mechanisms. This is a significant advantage.
- **Option c**: Both types of reactors can allow CO2 entry; this is not a distinguishing feature.
- **Option d**: While stirred-tank bioreactors may have automated features, they are not necessarily easier to operate than shake flasks.

4. **Conclusion**: Based on the analysis, the most significant advantage of stirred-tank bioreactors over shake flasks is that they provide better aeration and mixing properties. This is due to their design, which allows for efficient oxygen transfer and uniform mixing of the culture medium.

5. **Final Answer**: The correct answer is **option b: provide better aeration and mixing properties**.