Natural selection can lead to evolution in a population when: A. a new allele appears in one of the offspring in a new generation.
B. one of its individuals is able to obtain more resources than others.
C. all individuals have the same genetic traits as their parents.
D. it has genetically diverse members that compete for resources.

Im pretty sure the answer is A

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.