Which of the following are the main reactants required for the light-dependent reactions of photosynthesis?

• A. Glucose, oxygen (O\(_2\)), and ATP
• B. Water (H\(_2\)O\(), NADP\)^+\(, and ADP + P\)_i$
• C. Pyruvate, NAD\(^+\), and FAD
• D. Carbon dioxide (CO\(_2\)), NADH, and FADH\(_2\)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the context of the question. The light-dependent reactions of photosynthesis occur in the thylakoid membranes of chloroplasts and are responsible for converting light energy into chemical energy in the form of ATP and NADPH.
2. Step 2: Identify the main reactants involved in the light-dependent reactions. These reactions require water (H\(_2\)O) as a source of electrons, NADP\(^+\) as an electron carrier, and ADP + P\(_i\) to synthesize ATP.
3. Step 3: Recall the role of each reactant. Water (H\(_2\)O) is split during photolysis to release electrons, protons, and oxygen. NADP\(^+\) accepts electrons to form NADPH, and ADP + P\(_i\) are used to generate ATP through photophosphorylation.
4. Step 4: Eliminate incorrect options. Glucose, oxygen (O\(_2\)), and ATP are products of photosynthesis, not reactants in the light-dependent reactions. Pyruvate, NAD\(^+\), and FAD are involved in cellular respiration, not photosynthesis. Carbon dioxide (CO\(_2\)), NADH, and FADH\(_2\) are part of the Calvin cycle or cellular respiration, not the light-dependent reactions.
5. Step 5: Confirm the correct answer. The main reactants required for the light-dependent reactions are water (H\(_2\)O), NADP\(^+\), and ADP + P\(_i\), as these are essential for the processes of photolysis, electron transport, and ATP synthesis.