The rate of synthesis of organic matter by consumers is
(a) net primary productivity
(b) gross primary productivity
(c) standing state
(d) secondary productivity

Options

A. net primary productivity
B. gross primary productivity
C. standing state
D. secondary productivity

Answer

To solve the question regarding the rate of synthesis of organic matter by consumers, we need to analyze the given options carefully.

### Step-by-Step Solution:

1. **Understanding the Question**:
The question asks for the rate of synthesis of organic matter specifically by consumers. This means we are looking for a term that describes how consumers (organisms that eat producers or other consumers) generate or accumulate organic matter.

2. **Analyzing the Options**:
- **Option (a): Net Primary Productivity (NPP)**:
NPP refers to the amount of organic matter produced by primary producers (like plants) after accounting for the energy they use for respiration. This is not related to consumers, so this option is incorrect.

- **Option (b): Gross Primary Productivity (GPP)**:
GPP is the total rate of organic matter synthesis by producers before any respiration losses. Again, this is not related to consumers, making this option incorrect as well.

- **Option (c): Standing State**:
The standing state refers to the total amount of organic and inorganic materials present at a trophic level at a given time. It does not specifically measure the synthesis of organic matter by consumers, so this option is also incorrect.

- **Option (d): Secondary Productivity**:
Secondary productivity is defined as the rate of synthesis of organic matter by consumers. It measures how much energy is accumulated by consumers from the organic matter they consume. This is the correct option.

3. **Conclusion**:
Based on the analysis, the correct answer is **(d) secondary productivity**. This term specifically refers to the synthesis of organic matter by consumers.

### Final Answer:
**(d) secondary productivity**