In some viruses, RNA is present instead of DNA indicating that

Options

A. Their nucleic acid must combine with host DNA before replication
B. They cannot replicate
C. There is no hereditary information
D. RNA can act to transfer heredity.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question states that in some viruses, RNA is present instead of DNA. We need to determine what this indicates about these viruses.

2. **Analyzing the Options**:
- **Option A**: "Their nucleic acid must combine with host DNA before replication."
- This statement is incorrect. RNA viruses do not need to combine with host DNA to replicate. They can replicate using their own RNA or convert it to DNA through reverse transcription.

- **Option B**: "They cannot replicate."
- This is also incorrect. RNA viruses can replicate. They utilize the host's machinery for replication, and some can convert their RNA into DNA for replication.

- **Option C**: "There is no hereditary information."
- This statement is false. Both RNA and DNA serve as genetic material. RNA viruses still carry hereditary information.

- **Option D**: "RNA can act to transfer heredity."
- This option is correct. Experiments have shown that RNA can function as genetic material, meaning it can carry and transfer hereditary information.

3. **Conclusion**: Based on the analysis of the options, the correct answer is that RNA can act to transfer heredity.

### Final Answer:
The correct indication of the presence of RNA in some viruses is that RNA can act to transfer heredity.

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