Question

which statement describes a difference between the dark (light-independent) reactions and the light-dependent reactions?
○ light-independent reactions can only occur after sunset or during cloudy days, while light-dependent reactions only occur when it is sunny.
○ the light-dependent reactions occur in the leaves of plants, and the light-independent reactions occur in the limbs and trunks.
○ the products of the light-dependent reactions provide the energy to drive the light-independent reactions.
○ light-independent reactions store energy as atp and nadh, while light-dependent reactions store energy as glucose.

Explanation:

1. Analyze Option 1: Light - independent (Calvin cycle) doesn't require direct light but can occur during the day as long as products from light - dependent are available. Light - dependent need light but not just "sunny" (e.g., can occur on overcast days with light). So this is wrong.
2. Analyze Option 2: Both light - dependent (thylakoids in chloroplasts) and light - independent (stroma of chloroplasts) occur in leaves (chloroplast - containing cells), not limbs/trunks. So this is wrong.
3. Analyze Option 3: Light - dependent reactions produce ATP and NADPH (energy - carrying molecules) which are used by light - independent (Calvin cycle) to fix carbon into glucose. This is correct.
4. Analyze Option 4: Light - dependent reactions produce ATP and NADPH (store energy), light - independent uses them to make glucose (stores energy as glucose). So this statement has the processes reversed.

Answer:

The products of the light - dependent reactions provide the energy to drive the light - independent reactions.