Answer:
The complex chemical substances that are products of photosynthesis include carbohydrates. Here is a detailed explanation:
Photosynthesis:
- Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy.
- It occurs in the chloroplasts of plant cells, specifically in the chlorophyll pigment.
Products of Photosynthesis:
- The main products of photosynthesis are glucose (a simple sugar) and oxygen.
- Glucose is a carbohydrate and serves as the primary source of energy for plants.
- Oxygen is released into the atmosphere as a byproduct of photosynthesis.
Complex Chemical Substances:
- Carbohydrates are complex chemical substances that consist of carbon, hydrogen, and oxygen atoms.
- They are formed during photosynthesis through the combination of carbon dioxide and water in the presence of sunlight.
- Examples of carbohydrates produced through photosynthesis include glucose, sucrose, cellulose, and starch.
Other Options:
- Cellulose is a type of carbohydrate that provides structural support in plant cell walls.
- Vitamins are organic compounds that are necessary in small amounts for proper functioning of the body, but they are not directly produced through photosynthesis.
- Proteins are macromolecules composed of amino acids and are not directly produced through photosynthesis.
Therefore, the correct answer is Carbohydrate (Option B) as the complex chemical substances produced through photosynthesis.

Understanding Photosynthesis
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy, primarily in the form of glucose, using carbon dioxide and water. This process is essential for life on Earth, as it forms the basis of the food chain.

Products of Photosynthesis
During photosynthesis, several complex chemical substances are produced. The most significant among these is carbohydrates.

Why Carbohydrates?
- Definition: Carbohydrates are organic compounds made up of carbon, hydrogen, and oxygen, typically with a hydrogen-to-oxygen atom ratio of 2:1, similar to water.
- Types: The primary carbohydrate produced in photosynthesis is glucose. This simple sugar serves as a building block for more complex carbohydrates like starch and cellulose.
- Function: Carbohydrates are vital for energy storage and supply in living organisms. They are used by plants for growth and are also consumed by animals and humans as an energy source.

Other Options Explained
- Cellulose: Although cellulose is a carbohydrate, it is a complex form primarily used for structural purposes in plant cell walls.
- Vitamins: These are organic compounds that are not produced directly through photosynthesis, but are essential for various biological functions.
- Proteins: While important for life, proteins are made from amino acids, which are not direct products of photosynthesis.

Conclusion
In conclusion, carbohydrates are the primary products of photosynthesis, providing energy and structural components for various organisms. Understanding this fundamental process is crucial for grasping the interconnections within ecosystems.