Understanding the Passage and Blank 3

The passage describes the Sun and its vital role in our Solar System and for life on Earth. We need to find the most appropriate word to fill in the blank numbered (3).

The sentence containing blank (3) reads: "It is by far the most important (3) ______ of energy for life on Earth."

Let's examine the given options to determine which word best fits this context.

Analyzing the Options for Blank 3

The options provided are:

1. gesture
2. source
3. control
4. symbol

We need a word that describes how the Sun provides energy to Earth. Let's consider each option:

• Gesture: A gesture is a movement made to express meaning. This makes no sense in the context of energy.
• Source: A source is the origin or point from which something comes. The Sun is the origin of most energy on Earth. This fits the sentence perfectly.
• Control: Control means to direct or manage. While the Sun's energy influences Earth's climate and processes, the Sun itself isn't described as 'controlling' the energy in this phrase; it's where the energy comes from.
• Symbol: A symbol is something that represents something else. While the Sun can be a symbol (e.g., of warmth, life), in this scientific context describing its role, it is the actual origin of energy, not just a symbol of it.

Based on the meanings and the context of the sentence, "source" is the only word that logically completes the statement, indicating that the Sun is the primary origin from which energy for life on Earth is obtained.

Selecting the Most Appropriate Word

The sentence structure "(3) ______ of energy" requires a noun that indicates the origin or provider of energy. Among the options, "source" precisely means the point from which something originates or is obtained. The Sun is indeed the primary source of energy for Earth, driving processes like photosynthesis which are fundamental to life.

Therefore, the most appropriate word to fill in blank number (3) is "source".

Revision Table: Understanding Key Terms

Additional Information about the Sun's Energy

The Sun provides energy to Earth primarily in the form of electromagnetic radiation. This includes visible light, infrared radiation (heat), and ultraviolet radiation. This solar energy is crucial for many natural processes:

• Photosynthesis: Plants use sunlight to convert carbon dioxide and water into glucose (food) and oxygen. This process forms the base of most food chains on Earth.
• Climate and Weather: Solar radiation heats the Earth's surface and atmosphere, driving weather patterns and ocean currents.
• Water Cycle: Energy from the Sun causes evaporation, a key part of the water cycle.
• Renewable Energy: Technologies like solar panels convert sunlight directly into electricity, showcasing the Sun's potential as a clean energy source.

Without the Sun's energy, Earth would be a frozen, lifeless planet. Its role as a constant "source of energy" is undeniable.