Which of the following statements are correct to describe viruses?
I. Simple and unicellular organisms.
II.Contain DNA or RNA and enclosed by protein coat.
III. Possess own metabolic system and respond to stimuli.
IV. Maintain genetic continuity and undergo mutations.
The correct combination is

Options

A. I and II
B. II and IV
C. II and III
D. I and III

Answer

To determine which statements correctly describe viruses, let's analyze each statement step by step:

### Step 1: Analyze Statement I
**Statement I:** Simple and unicellular organisms.
- **Analysis:** Viruses are not classified as living organisms; they are acellular and require a host to replicate. Therefore, this statement is incorrect.

### Step 2: Analyze Statement II
**Statement II:** Contain DNA or RNA and enclosed by protein coat.
- **Analysis:** This statement is correct. Viruses can contain either DNA or RNA as their genetic material, and they are typically enclosed by a protein coat called a capsid.

### Step 3: Analyze Statement III
**Statement III:** Possess own metabolic system and respond to stimuli.
- **Analysis:** Viruses do not possess a metabolic system. They cannot carry out metabolic processes on their own and do not respond to stimuli like living organisms do. Thus, this statement is incorrect.

### Step 4: Analyze Statement IV
**Statement IV:** Maintain genetic continuity and undergo mutations.
- **Analysis:** This statement is correct. Viruses can maintain genetic continuity through replication and can undergo mutations, which allows them to evolve over time.

### Conclusion
Based on the analysis:
- **Correct Statements:** II and IV
- **Incorrect Statements:** I and III

The correct combination of statements that describe viruses is **II and IV**.

### Final Answer
The correct combination is **B (II and IV)**.

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