**Explanation:**

The creep rate in a ternary stage refers to the rate at which deformation occurs over time under a constant load and at elevated temperatures. Creep is a phenomenon that is commonly observed in materials such as metals, alloys, and polymers, and it is influenced by several factors including temperature, applied stress, and microstructure.

The correct answer to the question is option 'C' - the creep rate increases in a ternary stage. This means that as time progresses, the rate of deformation under a constant load and elevated temperature increases.

**Factors Influencing Creep Rate:**

Several factors influence the creep rate in a ternary stage. These factors include:

1. Temperature: Creep rate generally increases with increasing temperature. At higher temperatures, atoms and molecules have more energy, allowing for easier movement and deformation of the material.

2. Applied Stress: The creep rate is also influenced by the magnitude of the applied stress. Higher stress levels typically result in higher creep rates.

3. Microstructure: The microstructure of the material, including grain size and distribution, can affect the creep rate. Materials with finer grain sizes generally exhibit lower creep rates due to increased grain boundary resistance to deformation.

**Explanation of the Answer:**

In a ternary stage, the creep rate increases. This means that over time, the rate of deformation of the material increases under a constant load and elevated temperature. The reasons for this increase in creep rate can be attributed to several factors:

1. Temperature Effect: As the temperature increases, the energy levels of atoms and molecules in the material increase. This increased energy allows for easier movement of atoms, leading to a higher creep rate.

2. Stress Effect: The applied stress also plays a significant role in the creep rate. Higher stress levels result in a higher rate of deformation. In a ternary stage, the stress levels may be higher, leading to an increased creep rate.

3. Microstructural Changes: Over time, the microstructure of the material may undergo changes, such as grain growth or phase transformations. These changes can affect the material's resistance to deformation, leading to an increased creep rate.

Overall, the combination of increased temperature, higher stress levels, and microstructural changes contribute to the increase in creep rate observed in a ternary stage.