Answer: The correct answer for the fill in the blank is Light dependent phase of photosynthesis.
Photosynthesis ( synthesis of food in presence of sunlight) is primarily divided into Light dependent and light independent phase.
Light dependent phase occurs in the thylakoid membrane within chloroplast and the chemical reactions taking place in this phase are also called Hill reaction. Energy from sunlight is absorbed and converted into chemical energy in the form of ATP and NADPH and Oxygen is produced due to splitting of water in this phase.