Disguised unemployment:
Disguised unemployment refers to a situation where there are more workers engaged in a particular task than required. It is characterized by low productivity and underutilization of labor. In disguised unemployment, the marginal productivity of labor is zero because the additional laborers do not contribute to any additional output.

Explanation:
When there is disguised unemployment, it means that there are more workers employed in a task than necessary. This could be due to various reasons such as lack of alternative employment opportunities or lack of capital investment. As a result, the labor force is not fully utilized and there is underutilization of labor.

In such a situation, if one worker is removed from the task, the overall output will not be affected. This indicates that the marginal productivity of labor is zero. In other words, the additional worker does not contribute to any additional output, as the task can be easily completed by the existing workers.

For example, let's consider a scenario where a farmer needs only two workers to cultivate his land efficiently. However, he employs four workers for the same task. If two workers are removed, the output will remain the same, indicating that the marginal productivity of labor is zero.

In disguised unemployment, the excess labor is not contributing to any additional output. This type of unemployment is commonly found in the agricultural sector, where there is a surplus of labor, and the productivity of each worker is low.

Conclusion:
Disguised unemployment is characterized by underutilization of labor and low productivity. In this type of unemployment, the marginal productivity of labor becomes zero because the additional laborers do not contribute to any additional output. Removing one worker from the task does not affect the overall output, indicating that there is no marginal gain from employing additional labor.