To solve the question, we need to analyze the characteristics provided in the description and match them with the appropriate organism. Here’s a step-by-step breakdown:
### Step 1: Identify the Organism Type
The description states that it is a **single-celled organism**. This indicates that we are looking for either a type of bacteria, algae, or fungi, as viruses are acellular and do not fit this description.
**Hint:** Focus on the fact that the organism is single-celled to narrow down your options.
### Step 2: Assess the Color
The organism is described as having a **greenish color**. This characteristic is often associated with certain types of algae and cyanobacteria (commonly known as blue-green algae), which contain chlorophyll.
**Hint:** Think about organisms that are known for their green color due to chlorophyll.
### Step 3: Examine the Cell Structure
The organism has a **cell wall** around its cell membrane. This is a common feature in bacteria and algae. However, fungi have a different composition in their cell walls (chitin), which does not match the description.
**Hint:** Consider the types of organisms that have a cell wall and what materials they are made of.
### Step 4: Look at Membrane Infoldings
The description mentions **small infoldings of the cell membrane**, referred to as **mesosomes** in bacteria. This is a significant clue, as mesosomes are typically found in prokaryotic cells (bacteria).
**Hint:** Recall the structures present in prokaryotic cells that could match this description.
### Step 5: Analyze Genetic Material
The organism contains **genetic material in the cytoplasm** that is **devoid of any envelope**. This indicates that the genetic material is not enclosed in a nucleus, which is characteristic of prokaryotes (like bacteria).
**Hint:** Remember that prokaryotic cells have their genetic material freely floating in the cytoplasm.
### Step 6: Check for Ribosomes
The presence of **ribosomes for protein synthesis** is a common feature in both prokaryotic and eukaryotic cells. However, since we have already established that we are dealing with a prokaryotic organism, this aligns with our findings.
**Hint:** Ribosomes are essential for protein synthesis in all living cells, so this characteristic does not narrow down the options significantly.
### Conclusion
Based on the analysis:
- The organism is single-celled, greenish in color, has a cell wall, contains mesosomes, has genetic material without a membrane, and has ribosomes.
- The only organism that fits all these characteristics is **cyanobacteria** (blue-green algae), which is a type of bacteria.
**Final Answer:** The correct answer is **cyanobacteria** (option 2).
