The virologist .... Showed that the viruses could be crystallized .

Options

A. W.M . Stanley
B. T. O. Diener
C. M.W. Beijerinek
D. D.J . Ivanowsky

Answer

To solve the question "The virologist __________ showed that the viruses could be crystallized," we need to identify the correct virologist from the given options who was known for crystallizing viruses.

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a specific virologist who demonstrated that viruses could be crystallized.

2. **Review the Options**: The options provided are:
- A) W. M. Stanley
- B) T. O. Diener
- C) M. W. Beijerinck
- D) D. J. Ivanovski

3. **Analyze Each Option**:
- **Option A: W. M. Stanley**: He is known for his work on the tobacco mosaic virus. He successfully extracted, purified, and crystallized this virus, which was significant in virology. He was awarded the Nobel Prize for this work, making him a strong candidate for the answer.

- **Option B: T. O. Diener**: He is known for his work on viroids, which are smaller infectious agents. However, he did not crystallize viruses, so this option is incorrect.

- **Option C: M. W. Beijerinck**: He is credited with coining the term "virus" and discovering various viruses, but he did not crystallize any viruses. Therefore, this option is also incorrect.

- **Option D: D. J. Ivanovski**: He was the first to identify viruses but did not crystallize them. Thus, this option is incorrect as well.

4. **Conclusion**: After analyzing all the options, it is clear that the correct answer is **A) W. M. Stanley**, as he was the virologist who showed that viruses could be crystallized.

### Final Answer:
The virologist **W. M. Stanley** showed that the viruses could be crystallized.