<span>The products of the light-dependent reactions are used to help 'fuel' the light-independent reactions.
</span><span>Example:
NADPH and ATP are produced during the light-dependent reaction for use in the light-independent reaction (the Calvin Cycle). </span>
A should be the products and D should be the reactants. So D should be the answer.
The answer is A-Gravity. Why? This is because B and C are examples of chemical weathering and not mechanical. Although choice D may seem viable lava intrusion is not a direct cause of mechanical weathering although lava pushing upward may help in aiding mechanical weathering it would not be considered a big enough cause, thus gravity is the correct answer.
Answer is B. Releases heat and is exothermic