The correct answer will be- to synthesise the ATP molecules in respiration process.
Explanation:
The electron transport chain is the last phase of the cellular respiration which helps in the synthesis of a large number of ATP molecules.
The ATP molecules are synthesized when the energy generated by the movement of protons through CF₀ unit takes place.
The movement of electrons in the chain leads to the movement of proton from the mitochondrial matrix to the intermembrane space. This creates the proton gradient across the membrane which to equilibrate the protons move down the concentration gradient through ATP synthase. The energy while this is used to rotate the ATP synthase which coverts the ADP to ATP.
Thus, to synthesise the ATP molecules in the respiration process.
I would say C. Reduce climate change because taking a car/vehicle results in the earth becoming polluted which leads to climate change.
*EXPLANATION* Riding your bike or walking will not do anything to help people chopping down trees, people giving birth to more and more children nor will increase the amount of animals/organisms we have on our planet.