Which of the following is not a virus ?

Options

A. (a) Cyanophage
B. (b) T-phage
C. (c) E. coli
D. (d) `phi xx 174`

Answer

To determine which of the following options is not a virus, we will analyze each option provided:

1. **Sinophage**: This is a type of virus that specifically infects cyanobacteria (also known as blue-green algae). Therefore, Sinophage is a virus.

2. **T-phage**: This is another type of virus, specifically a bacteriophage that infects E. coli, which is a type of bacteria. Thus, T-phage is also a virus.

3. **E. coli**: This is a bacterium that is commonly found in the intestines of humans and other animals. It is not a virus but a living organism.

4. **5174**: This is a designation for a virus that infects E. coli, similar to T-phage.

After analyzing all the options, we can conclude that:

- **Sinophage** is a virus.
- **T-phage** is a virus.
- **5174** is a virus.
- **E. coli** is not a virus; it is a bacterium.

Thus, the answer to the question "Which of the following is not a virus?" is **E. coli**.

### Step-by-Step Solution:
1. **Identify each option**: Review each option provided in the question.
2. **Determine if each option is a virus**: Analyze whether each option is a virus or not.
3. **Conclude**: Identify which option is not a virus based on the analysis.