The smallest disease - causing agent is .... and it is made up of ……….
(a) (i) mycoplasma (ii) proteins and nucleic acids
(b) (i) prions, (ii) Proteins only
(c) (i) viroids, (ii) nucleic acids only
(d) (i) viroids, (ii) proteins only

Options

A. (i) mycoplasma (ii) proteins and nucleic acids
B. (i) prions, (ii) Proteins only
C. (i) viroids, (ii) nucleic and only
D. (i) viroids, (ii) proteins only

Answer

To solve the question regarding the smallest disease-causing agent and its composition, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the smallest disease-causing agent**:
- Among the options provided, we need to determine which agent is the smallest. The known smallest infectious agents are viroids, which are smaller than prions and mycoplasmas.

2. **Determine what viroids are made up of**:
- Viroids are composed of circular single-stranded RNA. They do not have a protein coat, which distinguishes them from other infectious agents.

3. **Review the options**:
- (a) Mycoplasma, proteins and nucleic acids: Mycoplasma is not the smallest agent.
- (b) Prions, proteins only: Prions are infectious proteins but are not the smallest.
- (c) Viroids, nucleic acids only: This matches our findings, as viroids are indeed made of RNA.
- (d) Viroids, proteins only: This is incorrect because viroids do not have proteins.

4. **Select the correct option**:
- Based on the analysis, the correct answer is (c) viroids, nucleic acids only.

### Final Answer:
The smallest disease-causing agent is **(c) viroids**, and it is made up of **nucleic acids only**.

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