which property of `CO_(2)` makes it of biological and geo-chemical improtance?

Options

A. Its acidic nature.
B. Its colourless and odourless nature
C. its low solubility in water.
D. Its high compressibility.

Explanation

To determine which property of carbon dioxide (CO₂) makes it of biological and geochemical importance, we can analyze the options provided:

1. **Acidic Nature**: Carbon dioxide can react with water to form carbonic acid (H₂CO₃), which is a weak acid. This property is significant in biological systems, particularly in maintaining pH levels in blood and other bodily fluids.

2. **Colorless and Odorless Nature**: While CO₂ is indeed colorless and odorless, this property does not directly relate to its biological and geochemical importance.

3. **Low Solubility in Water**: Carbon dioxide has low solubility in water, but when it does dissolve, it forms carbonic acid. This reaction is crucial for various biological processes, including respiration and photosynthesis.

4. **High Compressibility**: Although CO₂ is compressible, this property is not specifically linked to its biological or geochemical roles.

### Step-by-Step Solution:

1. **Identify the properties of CO₂**: Review the properties of carbon dioxide, focusing on its behavior in water and its role in biological systems.

2. **Analyze the acidic nature**: Recognize that CO₂ reacts with water to form carbonic acid (H₂CO₃), which can dissociate into bicarbonate (HCO₃⁻) and hydrogen ions (H⁺). This reaction is essential for buffering systems in biological fluids.

3. **Consider the importance of buffering**: Understand that the bicarbonate buffer system (HCO₃⁻ and H₂CO₃) helps maintain pH levels in biological systems, which is critical for enzyme activity and metabolic processes.

4. **Evaluate the other properties**: Assess the other options (colorless and odorless, low solubility, high compressibility) and determine that they do not have the same level of importance as the acidic nature of CO₂.

5. **Conclude with the correct option**: Based on the analysis, conclude that the acidic nature of CO₂, due to its ability to form carbonic acid and contribute to the bicarbonate buffer system, is the property that makes it biologically and geochemically important.

### Final Answer:
The property of carbon dioxide (CO₂) that makes it of biological and geochemical importance is its **acidic nature**, as it forms carbonic acid in water, contributing to the buffering system in biological processes.