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.
Surface tension is the property of water which allows for some lightweight insects to walk on top of a pond and not fall in. The molecules of water are held together by cohesive forces. The molecules of water present below the surface experience this cohesive force from all the directions, whereas the water molecules present on the surface experience a downward pull, as the force is not balanced. This leads to the concaving of the water surface inside a small tube.
Answer: B. Comparative embryology
Explanation: Good luck! :D