The light reaction of photosynthesis, also known as the photochemical phase, takes place in the thylakoid membranes of the chloroplasts. This phase requires several key components to occur, which include:

Chlorophyll (D): Chlorophyll is the pigment that absorbs light energy, which is crucial for the light reaction. When chlorophyll absorbs light, it becomes excited and this energy is used to convert $\mathrm{ADP}$ and $\mathrm{P_i}$ (inorganic phosphate) into $\mathrm{ATP}$ and to reduce $\mathrm{NADP}^+$ into $\mathrm{NADPH}$.

Light (E): Light provides the energy necessary for the excitation of chlorophyll electrons. Without light, the light reactions cannot take place.

$$\mathrm{H}_2 \mathrm{O}$$ (C): Water molecules are split during the light reaction in a process known as photolysis. This splitting produces electrons that replace those lost by chlorophyll, and it also generates oxygen as a byproduct.

While $\mathrm{CO}_2$ (A) is essential for photosynthesis, it is specifically used in the Calvin Cycle (dark reaction) and not directly required for the light reaction. $\mathrm{O}_2$ (B) is a product of the light reaction, not a requirement.

Therefore, the correct components required for the light reaction of photosynthesis are:

Option B: C, D, and E only.