Avery et al. used `:`

Options

A. Dnase
B. Rnase
C. Protease
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: Avery et al. conducted experiments to determine the nature of the genetic material in cells. Their work was pivotal in establishing that DNA, rather than proteins or RNA, is the genetic material.

2. **Experimental Setup**: Avery and his colleagues used a strain of bacteria known as Streptococcus pneumoniae. They used two types of this bacteria: one that was virulent (causing disease) and one that was non-virulent (not causing disease).

3. **Transformation Principle**: They discovered that when they mixed heat-killed virulent bacteria with live non-virulent bacteria, the non-virulent bacteria transformed into virulent bacteria. This indicated that some "transforming principle" was responsible for this change.

4. **Identifying the Transforming Principle**: To identify the nature of this transforming principle, Avery and his team systematically removed proteins, RNA, and DNA from the mixture. They then observed whether transformation still occurred.

5. **Conclusion**: The results showed that when DNA was destroyed (using DNase), the transformation did not occur. However, when proteins or RNA were destroyed, transformation still took place. This led Avery et al. to conclude that DNA is the genetic material responsible for heredity.

6. **Final Assertion**: Therefore, Avery et al. concluded that DNA is the substance that carries genetic information from one generation to the next, solidifying the role of DNA as the genetic material.