Solution:Concept- A change can be categorised as a chemical or physical change depending on how the properties of the subject change when it undergoes the change.
Now, a substance is said to undergo a physical change when only physical properties such as shape, size, colour, state or appearance of a substance change. Its chemical composition remains intact.
A substance is said to undergo a chemical change when the chemical properties of the substance change due to formation of new products.
Now, photosynthesis is the process through which plants convert light energy into chemical energy. In photosynthesis a chemical reaction is involved.
During the chemical reaction, water and carbon dioxide combine in the presence of sunlight to form glucose and oxygen.
As new chemical species are formed during photosynthesis, it is clear that photosynthesis is clearly a chemical change.
Hence, the correct option is (1).