Which of the following is not grouped with archaebacteria?
(a) Methanogens
(b) Cyanobacteria
(c) Thermophiles
(d) Halophiles

Options

A. Methanogens
B. Cyanobacteria
C. Thermophiles
D. Halophiles

Explanation

To solve the question "Which of the following is not grouped with archaebacteria?", we need to analyze each option provided:

1. **Understanding Archaebacteria**:
- Archaebacteria are a group of prokaryotic organisms that are distinct from eubacteria. They are known for living in extreme environments and are divided into several groups.

2. **Analyzing Each Option**:
- **(a) Methanogens**: These are archaebacteria that produce methane. They are indeed grouped with archaebacteria.
- **(b) Cyanobacteria**: This group is actually a type of eubacteria, not archaebacteria. They are photosynthetic and can be found in a variety of environments.
- **(c) Thermophiles**: These are archaebacteria that thrive in high-temperature environments. They are part of the archaebacteria group.
- **(d) Halophiles**: These organisms can live in high-salinity environments and are also classified as archaebacteria.

3. **Conclusion**:
- From the analysis, we can conclude that the only option that is not grouped with archaebacteria is **(b) Cyanobacteria**.

Thus, the correct answer is **(b) Cyanobacteria**.