Optimum temperature for photosynthesis is
A) 35°-40° C
B) 25°-35° C
C) 20°-25° C
D) 10°-15° C

Hint: Photosynthesis is the process of transforming solar energy into the chemical energy in the green plants and in certain other microbes. This process takes place in the chloroplast (cell organelle mainly found in the green part of the plant like in leaves).

Complete answer:
Chloroplast is also known as the kitchen of the cell present in every plant and is responsible for the process of photosynthesis. Photosynthesis is the biological process in which solar energy is converted into chemical energy when the optimum sunlight and temperature is given. During this process, light energy is captured and is used to convert water, carbon dioxide and minerals into oxygen and energy rich organic compounds that are necessary for the growth of the plants.
The process is truly dependent on three main factors. These are:
>Light irradiance(intensity) and wavelength
>Carbon dioxide concentration
>Temperature
>Water
The temperature required for photosynthesis varies from 10°-40° C depending upon the habitat. The optimum temperature required for photosynthesis ranges 25°-35° C.

Additional information:Photosynthesis process was discovered by Jan Baptist van Helmont into the 17th century. It is the process in which plants utilize water carbon dioxide and minerals and convert into the carbohydrate (glucose) and water in the presence of optimum temperature and sunlight.

Hence the correct option is ‘B’ i.e. 25°-35° C.

Note:Depending upon the utilization of carbon dioxide by the plants, plants are categorized into 2 parts:
>$C_3$ plants which cause carbon dioxide fixation only once like rice, wheat, oats etc.
>$C_4$ plants which cause the carbon dioxide fixation twice like maize, sugarcane, millet, sorghum etc.
Most plants, most algae and cyanobacteria are able to do photosynthesis thus they are called as phototrophs