How is starch made in plants?

Starch is a polysaccharide that plants synthesize as a way to store energy, primarily derived from glucose. The correct answer focuses on the process where glucose molecules are chemically bonded together to form starch. This occurs during photosynthesis, where plants convert carbon dioxide and sunlight into glucose.

Once glucose is produced, through a series of enzymatic reactions, multiple glucose units can be linked together in a condensation reaction to form starch. This ability to store energy as starch allows plants to accumulate excess glucose during periods of photosynthesis, which can later be broken down into glucose again when the plant needs energy for growth and development.

The other options do refer to various processes related to plant biology but do not accurately describe how starch is made. For example, while carbon dioxide and sunlight are involved in photosynthesis, they do not form starch directly. Instead, they are part of the initial process that leads to glucose production. Converting oxygen to carbon does not relate to starch synthesis either, as it misrepresents fundamental plant processes. Furthermore, while starch synthesis involves chemical reactions, the key point remains that starch is specifically made by joining glucose molecules.