The correct answer is option 'B': Region in the crust where hot molten rocks are trapped.

Explanation:
Geothermal energy is a form of renewable energy that is derived from the heat stored within the Earth. 'Hot spots' are regions in the Earth's crust where hot molten rocks are trapped, and they play a crucial role in the production of geothermal energy. Here is a detailed explanation of why hot spots are important for geothermal energy production:

1. Definition of Hot Spots:
Hot spots are areas in the Earth's crust where there is a concentration of heat due to the presence of molten rocks. These rocks are often referred to as magma when they are beneath the Earth's surface and lava when they reach the surface during volcanic eruptions.

2. Location of Hot Spots:
Hot spots are not evenly distributed around the world. They are usually found in certain regions where there is a higher concentration of volcanic activity. Examples of such regions include the Pacific Ring of Fire and the East African Rift System.

3. Heat Transfer and Geothermal Energy:
The heat from the hot spots can be harnessed to produce geothermal energy. This is done by drilling wells into the Earth's crust to access the hot rocks and the steam or hot water that they produce. The steam or hot water is then used to power turbines, which generate electricity.

4. Formation of Hot Spots:
Hot spots are formed by the movement of tectonic plates. As the plates move, they create cracks and fractures in the Earth's crust, allowing molten rocks to rise to the surface. This process is known as volcanic activity.

5. Geothermal Power Plants:
Geothermal power plants are built in areas where hot spots are present. These power plants utilize the heat from the hot rocks to generate electricity. They typically consist of wells, which tap into the underground reservoirs of hot water or steam, and powerhouses, where the steam or hot water is used to drive turbines.

6. Advantages of Geothermal Energy:
Geothermal energy is a renewable and sustainable source of energy. It does not produce greenhouse gas emissions or air pollution, making it environmentally friendly. It also provides a consistent and reliable source of power, as the heat from the Earth's interior is continuously replenished.

In conclusion, hot spots in the Earth's crust are regions where hot molten rocks are trapped. They are important for the production of geothermal energy as they provide a source of heat that can be harnessed to generate electricity. By tapping into the hot water or steam produced by these hot spots, geothermal power plants can produce a sustainable and clean source of energy.