Net Primary Productivity (NPP) is given by the formula

Options

A. NPP = GPP `xx 100`
B. NPP = GDP - secondary productivity
C. NPP = GPP - respiration rate
D. NPP = GPP/100

Explanation

### Step-by-Step Solution:

1. **Understanding Net Primary Productivity (NPP)**:
- Net Primary Productivity (NPP) is a crucial concept in ecology that represents the amount of organic matter (biomass) produced by photosynthetic organisms after accounting for the energy lost through respiration.

2. **Defining the Components**:
- **Gross Primary Productivity (GPP)**: This is the total amount of energy captured by photosynthetic organisms through photosynthesis.
- **Respiratory Loss (R)**: This is the energy lost due to the metabolic processes of respiration in plants.

3. **NPP Formula**:
- The formula for calculating NPP is:
\[ \text{NPP} = \text{GPP} - R \]
- This means that to find the NPP, you subtract the respiratory loss (R) from the gross primary productivity (GPP).

4. **Analyzing Options**:
- When presented with multiple-choice options regarding the formula for NPP:
- Option 1: NPP = GPP × 100 (Incorrect)
- Option 2: NPP = GDP - Secondary Productivity (Incorrect)
- Option 3: NPP = GPP - Respiration Rate (Correct, as Respiration Rate is equivalent to R)

5. **Conclusion**:
- The correct formula for Net Primary Productivity is:
\[ \text{NPP} = \text{GPP} - R \]
- Therefore, the third option is the correct representation of the NPP formula.